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René Descartes (1596-1650) is one of the most important Western philosophers of the past few centuries. During his lifetime, Descartes was just as famous as an original physicist, physiologist and mathematician. But it is as a highly original philosopher that he is most frequently read today. He attempted to restart philosophy in a fresh direction. For example, his philosophy refused to accept the Aristotelian and Scholastic traditions that had dominated philosophical thought throughout the Medieval period; it attempted to fully integrate philosophy with the 'new' sciences; and Descartes changed the relationship between philosophy and theology. Such new directions for philosophy made Descartes into a revolutionary figure.
The two most widely known of Descartes' philosophical ideas are those of a method of hyperbolic doubt, and the argument that, though he may doubt, he cannot doubt that he exists. The first of these comprises a key aspect of Descartes' philosophical method. As noted above, he refused to accept the authority of previous philosophers - but he also refused to accept the obviousness of his own senses. In the search for a foundation for philosophy, whatever could be doubted must be rejected. He resolves to trust only that which is clearly and distinctly seen to be beyond any doubt. In this manner, Descartes peels away the layers of beliefs and opinions that clouded his view of the truth. But, very little remains, only the simple fact of doubting itself, and the inescapable inference that something exists doubting, namely Descartes himself.
His next task is to reconstruct our knowledge piece by piece, such that at no stage is the possibility of doubt allowed to creep back in. In this manner, Descartes proves that he himself must have the basic characterisitc of thinking, and that this thinking thing (mind) is quite distinct from his body; the existence of a God; the existence and nature of the external world; and so on. What is important in this for Descartes is, first, that he is showing that knowledge is genuinely possible (and thus that sceptics must be mistaken), and, second, that, more particularly, a mathematically-based scientific knowledge of the material world is possible.
Descartes' work was influential, although his studies in physics and the other natural sciences much less so than his mathematical and philosophical work. Throughout the 17th and 18th Centuries, Descartes' philosophical ghost was always present: Locke, Hume, Leibniz and even Kant felt compelled to philosophical engage (often negatively, of course) with this philosophical giant. For these reasons, Descartes is often called the 'father' of modern philosophy.
This article provides an overview of Descartes' philosophical thought
following the order of his most famous and widely-studied book, the
Meditations on First Philosophy.
Table of Contents (Clicking on the links below will take you to that part of this article)
Descartes was born in a village near Tours in France in 1596. He was educated at a Jesuit college which was firmly grounded in the scholastic tradition, and by no means adverse to the study of either the humanities, or science. At the school he was given privileges similar to those enjoyed by boys of noble birth, but on the grounds of his fragile health. Descartes studied a broad range of subjects, and excelled particularly in mathematics. It is clear he benefited greatly from this Jesuit education, yet Descartes (in common with many intellectuals of his time) was keen to stress the separation of reason and faith. This meant that he could be sceptical concerning the philosophical and theological positions taken by the Church, while maintaining his Catholic faith. After taking a degree in law from Poitier, Descartes enlisted in the Dutch and, later, the Bavarian militaries. By 1619, under the influence of the Dutch mathematician and scientist Beeckman, Descartes began his exceptionally fertile mathematical studies of natural phenomena. Also around 1619, Descartes may have begun the unfinished Rules for the Direction of the Mind which was his first major philosophical treatise on the proper method for pursuing either science or rational theology. Over the next decade, Descartes alternated spending time in Paris with the circle of mathematicians and physicists gathered around the figure of Father Mersenne, and travelling widely. In 1629 Descartes moved to Holland where he lived in seclusion for 20 years, only occasionally returning to France, and changing his residence frequently to preserve his privacy.
The scientific and technical studies of these years resulted in the three texts on optics, meteorology and geometry, which were only published in 1637, and 'The World' which was published posthumously. Nevertheless, Descartes was establishing quite a reputation as a forbidable mathematician. Descartes made a number of important contributions to mathematics and physics, among the most enduring of which was his foundation (with Galileo) of what is now known as analytic geometry. That is, broadly speaking, the use of geometrical analysis to solve complex algebraic problems, and vice versa. It is difficult to overestimate the importance for the history of mathematical physics of this bringing together of the sciences of geometry and algebra.
With the exception of parts of the Rules and a few fragments, most of Descartes' early 'metaphysical' writings are lost. It was after he moved to Amsterdam that Descartes began working in earnest on the philosophical ideas upon which his fame now rests. The Discourse on the Method was published in 1637, together with the three treatises mentioned above. And in 1640, he enlarged upon the metaphysical issues therein, writing his Meditations on First Philosophy. The full title of this work is Meditations on the First Philosophy: In Which the Existence of God and the Distinction Between Mind and Body are Demonstrated. The work was first published in 1641 in Latin and was translated into French in the following year by the Duc de Luynes. The translation into French was relatively unusual and significant, for it testified to Descartes' wishes to bring his work to a wider, non-specialised audience, who lay outside the accepted 'authorities' on theological and philosophical matters. Descartes was so pleased with the French translation that he made some additions and fully endorsed it for later publication. Descartes passed a manuscript of his Meditations onto his friend, Father Mersenne, who solicited comments from fellow scholars, including Thomas Hobbes. The comments were returned to Descartes. These, along with his lengthy replies - several times longer than the Meditations themselves - were included in the second published edition of the Meditations (1642). The Principles of Philosophy followed in 1644.
In 1649, Descartes moved to Stockholm at the request of Queen Christina of Sweden who employed him as a philosophy tutor. Christina scheduled the lectures at 5 A.M. The early hours and harsh climate took their toll on Descartes's already weakened condition. He died shortly after in 1650. During his life, Descartes's fame rose to such an extent that (despite the theological controversies centering on him) many Catholics believed he would be a candidate for sainthood. As his body was transported from Sweden back to France, anxious relic collectors along the path removed pieces of his body. By the time his body reached France, it was considerably reduced in size.
Descartes' philosophy developed in the context of the key features of Renaissance and early modern philosophy. Like the humanists, he rejected religious authority in the quest for scientific and philosophical knowledge. Although Descartes was a devout Catholic, he was also influenced by the Reformation's challenge to Church authority, particularly the challenge against medieval Aristotelianism. Nevertheless, Descartes' philosophical vocabulary is heavily determined by scholastic thought - Descartes was happy to borrow ideas or principles where he felt they were not against clear reasoning. For Descartes, reason was both the foundation and guide for pursuing truth. He was an active participant in the scientific revolution in both scientific method and in particular discoveries. Finally, and perhaps most importantly, Descartes reacted strongly against the Renaissance resurgence of ancient Greek scepticism. Thus, we find in Descartes' writings a relentless pursuit of absolute certainty.
Descartes was hugely influential on individual, and key, philosophers throughout the 17th and 18th Centuries (Spinoza, Malbranche, Locke, Leibniz, etc.). His insistence on a radical philosophy that dispensed, as far as possible, with authority; his insistence on the perspective of consciousness in epistemology; his attempt to raise the standard of philosophical argumentation to a science akin to geometry; his close integration of philosophy and physical science; his emphasis on methodology, all were hugely important. Even philosophers who rejected his thought spent a great deal of time and energy doing so - Descartes could not be ignored. Though Descartes' mathematical works were unquestionably important, the particulars of his physics were less so. And yet Descartes' general physics - the rational justification for a universal, mathematical/ quantitative understanding of nature - was hugely significant. However, despite all these influences, his philosophical and scientific work never became the 'official' new philosophy, as he had hoped it would. First, it suffered condemnation, usually on religious grounds; this began already during Descartes' lifetime, and his work was officially 'prohibited' in 1663 by the Church in Rome. Then, by the early 18th Century, it suffered the double blow of the rise of empirically-minded approaches in Britain and France, together with the triumph of Newtonian physics pretty much everywhere.
The following article will provide an overview of the majority of Descartes'
philosophical ideas. For convenience, we will follow the order and structure of
his most famous and widely-read book, the Meditations on First
Philosophy. The fame and influence of this small book makes it unavoidable
as a guide to Descartes' thought. However, along the way and where appropriate,
a number of philosophical issues or alternative approaches from other key texts
will be introduced.
The Discourse on Method and Meditation 1
Context of Descartes' Method; Clarity and Distinctness
Descartes' philosophical method was also intended to be a method for science.
His concern with scepticism in all its forms was therefore directed not only at
religious scepticism, but at epistemological scepticism in general, according to
which any attempts to know the natural world must be doomed. We might
characterise Descartes' general position in the following way: the world created
by God was intended by Him to be known, provided only that human beings go about
the activity of knowing properly. How the activity of knowing might be properly
conducted is the issue of methodology.
Descartes' first discussion of scientific method is in an unfinished work of
1628 titled Rules for the Direction of the Mind. The first 12 of the
planned 36 rules deal with the general aspects of his proposed methodology, and
are considered early versions of principles that made their way into his later
writings. In 1633 Descartes prepared for publication a work on physics called
Le Monde which defended a heliocentric view of the universe. That same
year the Catholic Church condemned Galileo's Dialogue (1632). Descartes
did not think Galileo's views were prejudicial to religion and he worried that
his own views might be censured. Thus he suspended publication of it. In 1637
Descartes published a collection of essays titled Optics, Meteorology, and
Geometry. Prefaced to these essays was a work titled 'Discourse on the
Method of Rightly Conducting the Reason and Seeking Truth in the Sciences.' Most
of the 'Discourse' was written before the 1633 condemnation of Galileo's
Dialogue. However, he later added a concluding section that explained
that he insisted on publishing, in spite of political risks. The simple reason
was that he counted on the public to help confirm his scientific theories. In
the Discourse, Descartes offers a method of inquiry quite different from Francis
Bacon's as set out in the Novum Organum of 1620. Whereas Bacon advocated
induction, Descartes insists on a more deductive approach, focusing on the right
use of reason with respect to its own ideas.
Most of the Discourse is autobiographical insofar as it traces
Descartes intellectual development and how his method assisted him in his
investigations. It is important to realise, however, that the first person
'narration' frequently found in his philosophy is closely linked to Descartes'
philosophical project: how can the individual consciousness come to know itself,
its God, its world. Descartes realized that he needed to reject much of the
teachings of his youth. This raised the question as to exactly how he should
proceed in replacing old theories with new ones. He found his answer by analogy
with how old parts of cities are replaced with the new. The more elegant cities
are those which are methodically built from scratch, not those which continually
renovate old sections.
Descartes explains that he had learned a variety of methodological approaches
in a variety of disciplines. They all had limits, though. Syllogistic logic, he
believes, only communicates what we already know. Geometry and algebra are
either too abstract in nature for practical application, or too restricted to
the shapes of bodies. However, he believed that a more condensed and universal
list of methodological rules was better than a lengthy and varied list.
The second, to divide each of the difficulties I examined into as many
parts as possible and as may be required in order to resolve them better.
The third, to direct my thoughts in an orderly manner, by beginning with
the simplest and most easily known objects in order to ascend little by
little, step by step, to knowledge of the most complex, and by supposing some
order even among objects that have no natural order of precedence.
And the last, throughout to make enumerations so complete, and reviews so
comprehensive, that I could be sure of leaving nothing out. (I, 120)
What, however, is meant by the criteria of 'clarity' and 'distinctness' by
which Descartes describes the intuitive apprehension of simple natures and their
relations? In various works, Descartes has a number of attempts at defining
these important concepts. (E.g. Principles of Philosophy 1.45; cf also
Leibniz 'Meditations on Knowledge, Truth and Ideas (1684).) By 'clarity' is
meant something like the presence of an idea or object for attentive inspection
by the mind, so that all its qualities can be observed. Descartes often uses the
analogy of viewing a material object close up and in good light. By
'distinctness', on the other hand, is meant that the relationships between the
idea or object and anything else are themselves clear, such that what truly
belongs to the idea or object can be distinguished from its relationships. The
reader should also notice the phrase 'never to accept anything as true' in
Descartes' first rule. A quite radical initial procedure of doubting (testing
whether it can be accepted as true) thus forms part of Descartes' method. This
idea is pursued with the utmost ruthlessness in the Meditations.
Descartes realized that he needed a provisional set of moral guidelines to
carry him through the transition from abandoning his prejudices to establishing
the truth of things. He presents four such rules: (1) obey the laws of his
country and adhere to his faith in God, (2) to be consistent in following
positions, even if they seem doubtful, (3) change his desires rather than the
order of the world, (4) to choose the best occupation he could (i.e., that of a
philosopher).
Although Descartes' method had its advocates, it was also criticized by his
contemporaries, such as the mathematician Pierre de Fermat, and ultimately
dismissed. Leibniz says that Descartes' rules amount to saying 'take what you
need, and do what you should, and you will get what you want.' The first was never to accept anything as true if I did not have
evident knowledge of its truth; that is, carefully to avoid precipitate
conclusions and preconceptions, and to include nothing more in my judgements
than what presented itself to my mind so clearly and distinctly that I had no
occasion to doubt it.
Descartes commentator S.V. Keeling argues that Descartes'
method, as expressed in the above rules, rests on three mental operations:
intuition, deduction, and enumeration. These three abilities constitute our
human reason. Intuition involves directly apprehending the simplest components
(or 'simple natures') of a subject matter. Deduction is not merely syllogistic,
but a process of inferring necessary relations between simple natures.
Enumeration is a process of review which we use when deductions become so long
that we risk error due to a faulty memory.
| Type: | Objects | Properties |
| Secondary | Objects of Sense | hardness, heat, light, odour, colour, taste, sound |
| Primary | Objects of Mathematics | quantity, shape, time, magnitude |
An apple would be a secondary object, or object of the senses, when we consider only its secondary qualities of redness and sweet smell. On the other hand an apple is a primary object, or object of mathematics, when we consider only its primary qualities of shape and singularity (quantity). In Descartes' version of this distinction, the root of the primary/secondary distinction is the attribute of extension (or existence in space, including motion). All primary qualities are features that necessarily (and really) belong to extended objects. All secondary qualities, by contrast, do not necessarily (or really) belong to extended objects and, thus, are spectator-dependent. (Please compare the discussion beginning at Principles, part one, §48, I, 208ff.) However, it should be pointed out that Descartes has not yet offered a complete proof that extension is the key feature of spatial objects, and that all other properties are 'secondary'. Nor has he even proved that there are any spatial objects at all! He will return to extension and space towards the end of the Meditations. In any case, in view of this primary/secondary distinction, when Descartes doubts the reliability of his senses, he must find reason to doubt both his primary and secondary perceptions. The initial importance of this distinction, then, is that Descartes needs two sets of arguments in order to place into doubt the reality of both primary and secondary objects.
That which can be doubted is that which belongs to a class of 'knowledge' that has ever in the past failed, or which it can be imagined will fail under a (not impossible) hypothesis. Descartes begins his systematic doubting experiment by pointing out an obvious credibility problem with our senses: optical illusions. Descartes begins doubting the reliability of his senses by noting that we perceive distant objects to be much smaller than they really are. In other words, in some instances, the class of sensory knowledge has been known to break down; and for this reason, it can never be absolutely trusted. This, though, is somewhat trivial, and does not undermine the general reliability of the senses, since it is precisely through other sensory knowledge that we know that the object is further away. If the class of sensory knowledge is self-correcting in this fashion, it is perhaps not radically unreliable. Continuing his doubting experiment, Descartes suggests the possibility that he his dreaming. Here, Descartes is proposing a hypothesis, which is not intrinsically impossible (I am dreaming even though I believe myself to be awake), but which calls into question the basic validity of the class of sensory knowledge. This, though, only brings into question the existence of objects of the senses (i.e., secondary qualities), and does not affect objects of mathematics (i.e., primary qualities). The basic mathematical principles of space and time, Descartes says, are the 'components' from which my elaborate dreams are constructed - and as such cannot be doubted along with the existence and secondary qualities of the particular objects, on the basis of the dream argument.
Taking his doubts further, Descartes initially speculates that God is deceiving him about all of the things that he believes or perceives. This would happen if God were actively putting ideas into my head that, prima facie and in all cases, seemed to have some other source. (The notion of deception, as Descartes is using it here is more limited that that which he employs from Meditation 4 onwards. Please see Meditation 4 for our discussion of commissive and omisive deceptions.) Descartes includes primary objects in this hypothetical deception - thus, God deceives me even about the ideal objects of mathematics. Descartes writes:
... [S]ince I sometimes believe that others go astray in cases where they think they have the most perfect knowledge, may I not similarly go wrong every time I add two and three or count the sides of a square, or in some even simpler matter, if that is imaginable? (II, 14)Suggesting that God is a deceiver causes him problems, though, because according to traditional Christian theology, infinite goodness is one of God's necessary attributes. Goodness and deception seem opposed. If backed into a corner, some might deny God's existence rather than admit that he is the cause of deception. And yet, denying God, Descartes argues, could only make him more vulnerable to deception. This takes him into a discussion of scepticism, and he reflects on how far astray his doubts may take him, and to what extent they are justified. Discussions of scepticism during the modern period often drew a distinction between speculative and actional scepticism. A speculative sceptic merely uncovers theoretical problems, and an actional sceptic continues by recommending a course of action. With religious beliefs in particular, actional scepticism was viewed as more dangerous as it might recommend that act as though there were no God. However, Descartes only proposes theoretical doubt. In any event, he revises his doubt so not to run counter to traditional Christian belief and, accordingly, proposes that a malevolent demon or genius (and not God) deceives him. Simply considered as hypotheses, there is no way of comparing the plausibility of the existence of an infinitely good deity, with the existence of a malevolent demon.
With the demon hypothesis, Descartes' procedure doubt has reached its peak. Such a demon could cause ideas to appear within Descartes' mind such that he was deceived not only about the existence and nature of secondary qualities, but even about the existence and nature of primary qualities. It follows that if there is to be knowledge, then either there must be a new, as yet unmentioned ground of knowledge, or new reasons must be found that independently remove the above doubts. In either case, there must also be a means of testing (a 'rule of truth') whether such knowledge is indeed beyond doubt. Descartes' philosophy now moves to explore such issues.
There are, however, a few features of Descartes' method of doubt that are worth pulling out at this point. First, and reasonably enough one might think, Descartes never doubts that his ideas arise in some fashion. The source might be external objects, or his own dreams, or a hidden faculty of self-deception, his own activity of thinking, or God, or an evil genius. (This problem of the sources of ideas corresponds with the notion of a 'class' of knowledge introduced above.) Because there are so many possible sources for my ideas, and because there is no fool-proof way of deciding between them, Descartes is able to doubt the veracity of most of the ideas he formerly held to be true. This question of the origin of his ideas is key. For, in Meditation 6, Descartes will be able to solve his initial epistemological scepticism by eliminating all but one of the sources. (Moreover, the question of the origin of ideas also forms the basis of Descartes' proof for God's existence in Meditation 3.)
Second, Descartes is offering a broadly representational picture of how ideas
might relate to reality. Ideas of particular objects 'represent' the world. This
in turn has several consequences. (a) Ideas are different from things in the
world. (This already moves Descartes towards a broadly realist epistemology, and
thus can be interestingly contrasted with the idealism of Berkeley.) (b) Ideas
(at least of secondary qualities) do not resemble the world: my idea or feeling
of hunger (to take one of Descartes' favorite examples) has no resemblance to
whatever may be happening in my stomach, if I have a stomach. Because of this
lack of resemblance, there is no intrinsic difference between an idea that does
not correspond to a real world, and one that does. Without that intrinsic
difference, Descartes is initially unable to trace his ideas of things back to
their source. (The situation is more complicated in the case of primary
qualities, however. Although my idea of a triangle is not triangular,
nevertheless Descartes suggests it does have a relation of adequacy that ideas
of secondary qualities often or always lack [see the beginning of Meditation
5].) Issues of this type, as we shall see, lead Descartes to worry about the
notion of innate ideas. (c) Finally, representation means that there are two
different ways in which an idea can be 'false'. First, it can represent real
things falsely (as in the case of distant objects appearing smaller). Second, it
can represent as existing things that do not exist. Again, there is no intrinsic
way of distinguishing between these cases. Our inability to distinguish between
these two types of falsehood is what makes the dreaming and malevolent demon
hypotheses so powerful. For, if in any case I could so distinguish, then I would
be able to eliminate some of the hypothetical sources of my ideas. Descartes'
concerns about the various modes of falseness return in his discussion of
judgement and will, beginning in Meditation 3. Metaphorically speaking, we might
say that this representational model of the relation between ideas and the world
has placed Descartes 'at a distance' from his world, and made both possible and
necessary the method of doubt.
Meditation 2
Descartes opens Meditation 2 by describing the extent of his doubt. Virtually
every item of knowledge he previously believed is subject to some kind of doubt
for reasons given in the previous meditation. The ancient Greek engineer
Archimedes said 'give me a fulcrum and a firm point, and I alone can move the
earth.' Analogously, Descartes believes that if he finds one indubitable truth,
together with a means for employing it, then this will be the foundation of a
true philosophical system. The 'firm point' is his existence: 'this proposition,
I am, I exist, is necessarily true whenever it is put forward by me or
conceived by my mind' (II, 17). Even an evil genius cannot deceive him in this
matter. In his Discourse on the Method, Descartes summarizes his line of
reasoning in the famous phrase, 'I think, therefore I am' (or in Latin, 'cogito
ergo sum'). (The 'fulcrum' - or as we expressed it above, the 'means for
employing' his foundation - is clarity and distinctness, which we discussed
above in the context of Meditation 1. Descartes will be employing this 'rule of
truth' throughout the Meditations, although he is not fully explicit
about its importance until the beginning of Meditation 3.)
Descartes borrowed this strategy from Augustine's attempt to refute
scepticism in his own day. Augustine writes, 'On none of these points do I fear
the arguments of the sceptics of the Academy who say: what if you are deceived?
For if I am deceived, I am. For he who does not exist cannot be deceived. And if
I am deceived, by this same token I am' (City of God, 11:26).
Much of the philosophical debate about Descartes' famous move revolves around
how it is appropriate to analyse Descartes' argument, and even whether it is an
'argument' as such at all. For example, we might think that Descartes move is a
miniature argument, which would go from 'I think' to 'I exist'. But that assumes
a missing premise, namely, that 'Thinking things exist'. Descartes himself helps
clarify this in his reply to the second Objections to his Meditations. In
these Objections, the critic contends that all demonstrative knowledge depends
on God, which isn't proven until Meditation 3; but, Descartes deduces his
existence in Meditation two. Descartes replies that the cogito is not deduced,
but is recognized, in any particular case, by a simple and immediate act of
mental intuition. The intuition exhibits perfect clarity and distinctness.
Presumably, this is one of the notions Descartes has in mind when using such
phrases as 'whenever' I think, I must exist (Meditation 2, II, 17)) - or
similarly 'at the same time as' I think, I must exist (Principles part
one, §7, I, 195)). From such simple intuitions, we can then generalise in order
to say 'thinking things exist', but the generalisation is founded on our
initial, simple intuition. Descartes makes a similar point about general or
abstract knowledge concerning what is thinking, or what is existing, in the
sixth Replies. Such knowledge is always preceded by, and grounded on, unmediated
'inner awareness'.
Once Descartes recognizes the indubitable truth that he exists, he then
attempts to further his knowledge by discovering the type of thing he is. Trying
to understand what he is, Descartes recalls Aristotle's definition of a human as
a rational animal. This is unsatisfactory since this requires investigating into
the notions of 'rational' and 'animal.' Continuing his quest for identity, he
recalls a more general view he previously had of his identity, which is that he
is composed of both body and soul. He can't refer to himself as a thing that has
a body, though, since this involves sensory perception. According to classical
philosophers such as Plato and Aristotle, the key attributes of the soul involve
eating, movement, and sensation. He can't claim to have these attributes of the
soul since this involves a body, knowledge of which, in turn, is based on the
senses. Descartes continues examining other theories of human existence and
attributes about himself that he can imagine. Descartes concludes that the
attribute of thinking is the only quality that he can justifiably claim at this
point. But he is quick to point out that thinking is the only attribute about
which he is sure - not that thinking is the only attribute that he has. I
am, then, at least a thing that thinks.
Despite this caution, the attribution of thought to the soul is the starting
point of a radical ontological distinction which carries Descartes through his
Meditations. That distinction is between thinking substance (res
cogitans) and extended substance (res extensa). The two substances
are mutually exclusive. A thinking substance is nonphysical or spiritual in
nature, and an extended substance is physical, but not capable of consciousness
or thought. Descartes has not yet offered proof of these ideas, but the reader
should keep them in mind. For Descartes, a thinking thing is 'a thing which
doubts, understands, [conceives], affirms, denies, wills, refuses, which also
imagines and feels.'
Note Descartes' general strategy for adding to his knowledge. He is first
concerned with the issue of our inner, mental nature, and will only much later
address the issue of external objects (in Meditation 6). As we noted above, this
ties in nicely with the first-person 'narration' of many of his philosophical
works. Descartes then anticipates the criticism that he is going about his
investigation backwards. For, it seems that knowledge of external objects is
more obvious and distinct than knowledge of the mind, and much more
obvious than knowledge of my personal identity (the continuity or sameness of
the mind as it thinks now this, now that). Everyone knows what an apple is (an
external object), but few people can properly answer the question 'who am I'.
Thus, it seems that Descartes should tackle the easier problem of external
objects first.
Descartes does not agree that he proceeding in a backwards fashion, and
argues that the properties and identity of our mind are actually more clear and
fundamental than perception of external objects. He makes his case by comparing
our perceptions of a piece of wax at two times: once while the wax is in a solid
state, and later after the wax has been melted by a fire. Between these two
states, the wax somehow loses its hardness, colour, shape, odour, and so forth.
That is to say, we must forgo all the sensible properties that might allow us to
identify it as the same substance. Thus, our senses alone cannot inform us of
the continuity of the two states of the wax, so what does? The continuity of the
wax cannot be established though the faculty of the imagination either, since we
could imagine an infinite variety of changes the wax could go through - and
however powerful my faculty of imagination it is not infinite. Descartes
concludes that the continuity of the wax is established neither by sight, nor
touch, nor imagination, but by an act of the mind alone. Knowledge within the
mental realm precedes knowledge of the material realm.
Descartes considers possible criticisms to his conclusion that we understand
the physical world through an act of the mind. In common language we claim that
we 'see' the same wax in its two states (as opposed to 'mentally intuit' the
same wax in its two states). Thus, common language seems to suggest that the
continuity of the wax is a function of 'seeing' (i.e., the senses). When I look
out the window, I conclude that we see people crossing the road. All that
appears to my senses, though, is clothing; and why could the clothing not be
covering machine: automata or 'robots'? Nothing in the senses renders that
unlikely; the judgement that these are people (or the judgement that this is
still wax, and the same piece of wax) is 'actually grasped solely with the
faculty of judgement, which is in my mind.' Furthermore, even if Descartes'
analyses are wrong, even if he determines through sight or imagination that the
wax continues after all, then this still presupposes that Descartes himself
exists and thinks. However you cut it, the direct awareness of the mind is prior
to any awareness of external objects. Meditation 3
Descartes notes that when he contemplates the certainty of his existence, he
knows the truth of his existence clearly and distinctly. He proposes a general
rule: everything he perceives clearly and distinctly is true. This rule has in
effect been in operation throughout the previous discussions. Descartes would
like to use this general rule in order to move beyond the 'I think, I exist',
for example to show both the existence of external objects and the truth of
mathematics. Unfortunately, knowledge of external objects does not rise to the
level of clarity and distinctness. Sensory judgments about particular things in
the external world at first seemed vivid and immediate, but later proved to be
questionable. By contrast, mathematical judgments are perceived in a manner that
appears to be clear and distinct. Such judgements were thus able to pass
unscathed through most of the tests in the procedure of hyperbolic doubt.
However, an obstacle remains: it is still just possible that God may be
deceiving him irrespective of this initial appearance of clarity and
distinctness. To put the general rule of clarity and distinctness on sound
footing, Descartes must (a) prove God's existence, and then (b) show that God is
not a deceiver. It thus appears that, important as it is for other reasons, the
proof for God's existence is not really a central issue of the
Meditations but is merely a device for establishing methodology.
In constructing his argument for God's existence, Descartes makes several
prefatory comments about the nature and content of human thought. He begins by
outlining the various types of thoughts we have, which include ideas, thoughts,
volitions and judgments. Descartes distinguishes between: (i) Images (ideas)
(e.g. soup); and (ii) the manner of our having the images or ideas. Of the
latter, he distinguishes between 'volition' ('I desire the soup'), affections
('The soup tastes good'), and what he calls 'judgements' ('There is soup in the
bowl' or 'the soup made me feel better'). Only judgments have a truth value,
Descartes argues, and consequently most deception comes about through bad
judgments about ideas. That is to say, we can distinguish between all of the
ideas that make up a judgement, and the judgement itself. The ideas themselves
cannot really be true or false; only in special cases where an idea stands for
something that is, in reality, a negation or absence (e.g. the ideas of cold or
vacuum) and thus literally represents nothing, can we say that it is
'materially' false. (Note that 'unicorn' is not materially false; it represents
a possible object that happens not to exist.) For the most part, it is the
judgements we make about ideas that are true or false ('formally' true or
false): e.g. 'There is a unicorn in your rose garden' is (probably!) false. (We
might speculate on Descartes' behalf that the idea of my own thinking, on the
other hand, might be unique in being the only idea that immediately leads to an
existential judgement: 'I exist'.)
There are three kinds of ideas, Descartes continues: fictitious (invented),
adventitious (from external objects), and innate (inborn). We can be pretty
certain that some instances of the first class exist, but cannot be certain yet
about the other two classes (because of the issues discussed at the end of the
section on Meditation 1). Thus, a final prefatory issue concerns the
adventitious ideas (that is, ideas of external objects). Are they really
produced by external objects as they seem to be? One reason why we believe
adventitious ideas have their origin in physical objects (as opposed to being
mere fictions of the mind) is because we are taught this by nature. Descartes
believes that nature teaches us in an unabsolute sense (that is, by a
spontaneous impulse) that adventitious ideas are caused by external objects.
Feeling discomfort, we 'naturally' draw away, just as if the source of the
discomfort and our bodies were both real objects in space. As philosophers,
however, we cannot just trust natural impulses, since they often lead us astray,
such as with moral intuitions. Another reason why we believe adventitious ideas
have their origin in external objects is that these ideas are independent of our
will or volitions. We may not rely on this reason, though, since we may have an
unknown mental faculty that produces such ideas without the corroboration of our
conscious will. Descartes next argues that even if adventitious ideas were
caused by external objects, an idea may in no way resemble the object
causing it. He illustrates this problem with our two ideas of the sun: the
visual one and the intellectual one derived from the mathematical study of
astronomy. The latter, although less a straight-forward 'picture' of the object,
probably 'resembles' the real sun more accurately. (This again goes back to
primary and secondary qualities.) Descartes concludes that only a 'blind
impulse' makes us believe that adventitious ideas correspond to real physical
objects.
Since adventitious ideas have no clear basis in external objects, Descartes
cannot attempt to prove God's existence through a posteriori arguments (that is,
arguments based on our perception of external objects). For example, he cannot
argue for God's existence based on apparent design in the world, since he cannot
trust his (apparently) adventitious ideas of design. However, there is another
path open to him: as we saw above, he can rigorously separate the ideas we have
from the judgements we make about whether and how the represented objects exist.
Thus, he can simply examine the content of his ideas, ignoring their connection
with external objects. In his words, he will consider his ideas as merely 'modes
of thought.'
The first step in applying this new procedure is to discuss a principle of
causality: 'there must be as much in the total efficient cause as there is in
the effect of that same cause.' The notion of 'efficient cause' refers to
Aristotle's analysis of causation, which was also widely taken up in Medieval
philosophy. However, while in Aristotle, efficient causes were of secondary
importance metaphysically, in Descartes efficient cause becomes practically
equivalent to cause per se. (Another example of Descartes' new approach
vis a vis Medieval thought concerning the physical world.) An 'efficient
cause' of X refers to the entity that incites the change that is, or leads to,
X. Thus 'total efficient cause' refers to the collection of entities that,
together, bring about the thing. (Although we might say that a single word can
cause a war, the word by itself would not be the total efficient cause.)
Descartes is basically claiming that the cause must be adequate to incite or
bring about the effect. For example, if an object has 5 units of heat, then its
total cause must have at least 5 units of heat. (The heat of course could be in
a different form: as potential or chemical energy.) This principle traditionally
has been called the principle of sufficient reason, and he believes that
we know this innately. Similarly, Descartes argues that something that is unreal
can not (on its own) bring about a thing that is real; or again, something
simple cannot (on its own) bring about something complex.
Extrapolating from these principles and definitions, Descartes claims that
something that is less perfect can not (on its own) bring about a thing that is
more perfect. By 'perfection' is meant, let us say, the hierarchical level of a
thing within the hypothetical createdness of all things; that is, its relation
vis a vis the infinite mind, infinite goodness, etc. of God. Now,
importantly, we can talk about perfection in this way even though we have not
proved the existence of God. For, in a similar way, we can say that someone is a
more perfect cook than someone else, even though no one exists who is the
perfect or ideal cook. In this case, though, unlike the idea of God (Descartes
thinks) the idea a perfect cook arises because we extrapolate from greater or
lesser cooks of our experience. This idea of perfection is related to the notion
of a degree of reality (and Descartes often speaks in those terms) in so far as
the perfect being is thought to have a self-caused or necessary existence,
whereas 'lesser' beings are considered 'contingent'. Moreover - and although
Descartes has not yet proved this yet - it seems to make sense to say that
primary qualities are more real than secondary qualities, and that the
substances that have those primary qualities are more real than the qualities in
themselves, and so forth. Furthermore, the idea of perfection is related to the
notion of complexity by way of what Augustine called the principle of plenitude:
the cosmos (and thus its creator) is the greater the more complex it is.
Descartes argues that the principle of sufficient reason applies to ideas as
well as to physical objects. In order to understand his discussion we need to
distinguish between three ways of speaking of the level of reality or
perfection. First, something contains a degree of perfection 'formally' if it
contains that degree in itself, and is capable of causing such a degree of
perfection in another thing. Second, something contains a degree of perfection
'eminently' if it contains a greater degree and is thus capable of causing at
least the degree. Third, something contains a degree of perfection 'objectively'
or 'in representation' if it is an idea of something that is represented as
containing such a degree of perfection. (See Descartes' reply to the second
Objections (II, 113-4).)
Now, when we view ideas merely as modes of thought, one of the features by
which ideas differ from one another is that some seem more perfect or complex
than others. In Descartes' terminology, a more perfect or complex idea has
greater objective reality than a less perfect or complex idea. For
example, ideas of eternal substance, such as God, have more perfection than
ideas of finite substance, such as trees or dogs. To apply it to our ideas and
the qualities those ideas exhibit merely as modes of thought, Descartes
reformulates the principle of sufficient reason to say that the cause of an idea
must have reality formally or eminently as the idea has reality objectively.
That is, an idea with a moderate amount of objective reality (let's say, with
five units of complexity) must be produced ultimately by something with at least
that much formal reality (five or more units of complexity). Based on the
principle of sufficient reason as it applies to ideas, Descartes believes that
there are important conclusions we can draw about the origin of specific ideas.
Descartes believes that his ideas of people, animals or even angels could have
arisen from within himself since they can arise from ideas of himself. He
continues discussing the origins of ideas of physical objects, particularly
regarding their secondary and primary qualities. He believes that his ideas of
light, colors, sounds, odors, tastes, and heat (that is, secondary qualities)
need no explanation outside of himself. Primary qualities too, such as
substance, duration, and number, may also be explained by the idea of himself.
If it turned out that a hidden faculty of idea-production in his mind produced
all these ideas, that would not contradict the principle of sufficient reason.
Finally, Descartes considers the idea of God that is in his mind. This idea
is that of 'an infinite and independent substance,' that is infinitely perfect.
Where does this idea come from? Such an idea requires an explanation beyond
himself, because Descartes himself is a finite and thus imperfect being - the
fact that he can doubt is proof enough of that. (It is impossible to imagine God
having doubts.) Moreover, that explanation must have as much formal reality as
the initial idea of infinite perfection. This, then, is his proof for God's
existence: Descartes addresses three possible criticisms of his argument. Each of these
possible criticisms suggests that our idea of infinite perfection need not be
caused by God himself. A first possible criticism is based on Descartes'
assumption that we initially possess an idea of the infinite, and that our idea
of the finite consists of the negation of our idea of the infinite. A critic
might argue that the opposite is the case: we have an initial idea of the finite
and our idea of the infinite is its negation. (Just as we assumed in the example
of the perfect cook above.) In this case, we could be the cause of infinite
perfection by (a) taking the idea of finite imperfection from ourselves, and (b)
negating this idea. However, both the idea of a cook, and the idea of a perfect
cook, are finite ideas (involving only finite complexity, for instance). To
arrive at the latter by the negation of the limits of the former is a possible
operation for a finite mind. (There is a relation here to Anselm's reply to
Guanilo's objection concerning the perfect island, in their debate on the
ontological argument.) But the idea of God is not a finite idea in this sense,
and cannot be arrived at by a finite mind through negation of finite ideas any
more than by way of the positive imagining of ideas. (See also the Fifth
Objections and Replies (II, 252).)
A second possible criticism is that the idea of infinite perfection is
'materially false and can therefore be from nothing.' More simply, the
suggestion is that the idea of infinite perfection is an incoherent concept, and
thus needs no explanation beyond itself. However, Descartes argues that the
notion of infinite perfection is clear and distinct in the highest degree, and
thus requires an explanation. (Descartes and Arnauld continue the discussion of
this problem in the Fourth Objections and Replies.) A third possible criticism
is that perhaps we are potentially infinitely perfect, and thus produced the
idea of infinite perfection from our hidden potential. Descartes gives three
replies to this third criticism. First, if his potential perfection can be
actualized only gradually (through a gradual increase in knowledge), this
implies that he is finite. And, if he is a finite being, he could not produce
the idea of infinite perfection. Second, he argues that even if his knowledge
would increase gradually over an infinite amount of time, at no point would he
have infinite knowledge. Third, he argues that the objective being of an idea
cannot be produced by a merely potential being.
Another criticism raised in the Fifth Objections (II, 205ff) is that it is
impossible for a finite mind to comprehend an infinite idea of God, just as (in
Descartes' account) it is impossible for a finite mind to generate an infinite
idea. In other words, human beings do not have an idea of God in the sense
needed by Descartes' argument. Descartes replies by distinguishing between a
fully adequate idea of something (which he claims a finite mind cannot have even
of the most simple entity) and an 'understanding suited to the scale' of our
finite intellect. In other words, of course our positive idea of God's infinity
is not an adequate comprehension of God, but it is sufficient for us to know (a)
that the idea could not have originated with us; and (b) that it is the idea
of an infinitely perfect being. In the 'Preface' to the Meditations,
Descartes discusses a criticism of this argument as it appeared in the
Discourses (II, 7). There, he implicitly makes a similar distinction
between the finitude of the ideas of our minds, and the possibility of finite
ideas representing infinite entities (and thus having non-finite objective
reality).
Following a similar line of reasoning, Descartes concludes at the end of
Meditation 5 that this idea of God must be innate in him, as 'the mark of the
craftsman stamped on his work' (II,35). It is from this unfalsifiable mark,
then, that God's existence can be known. Recall our discussion of Descartes'
views on the representational nature of mental contents, at the end of the
section on Meditation 1 above: the idea of God is the only idea the mere inner
characterisitics of which allow us to deduce with certainty the origin of the
idea.
We should note that, despite its concern with 'perfection', this argument
must be accounted a version of the cosmological argument, because of its central
concern with causes and effects. Descartes also provides a version of the
ontological argument in Meditation 5.
Descartes is quite happy with these arguments, but he admits that their
abstract quality means it is difficult for him to remain convinced once his
concentration has wandered. How, some time after thinking through the argument,
can we remain sure that it is sound? Descartes now wishes to show that God is
the cause of his existence. If Descartes can show that even his own existence
(as a being that has an idea of God) depends upon God, then that will lend to
his certainty about God's existence the same utter transparency he has
concerning his own existence and the existence of his ideas. But there is
another important reason for the discussion of the dependence of his existence:
by showing the connection between God and himself, Descartes can argue that by
virtue of that connection it must be impossible for his memory to be
systematically flawed. If memory is reliable, then (in general) one can rely
upon the memory of proving something, even after one's attention has wandered.
This, as we shall see, is of the utmost importance, for otherwise, having to
keep reiterating the same arguments over and over, it would be impossible for
the philosopher to progress.
Descartes constructs the argument through a process of elimination, arguing
that strictly speaking he could not be produced by (a) himself, (b) a finite
cause less perfect than God, (c) by several partial causes, or (d) by his
parents. God is the only possible cause for his existence. The others can easily
been seen as either inadequate or fragmentary explanations.
Descartes gives two replies to the suggestion that he was derived from
himself. His first reply is that if he caused himself, then he would be God
since he would give himself every perfection he could. Descartes' second reply
is based on the fact that he exists over time. Each of the parts and moments of
his existence depends on others. He then asks whether 'I possess some power
enabling me to bring it about that I who now exist will still exist a little
while from now?' He answers that he does not have the power in himself for
duration, so it follows that he doesn't have the power for creation either
(these two powers being not really distinct). (This point is particularly
significant since it allows Descartes to argue against seeing the series of
contingent causes as an infinite regress: that which sustains my existence must
be a real, necessary, first cause.) A further suggestion is that he was caused
by a finite cause less perfect than God. He responds noting that this finite
cause would have to possess the idea of infinite perfection too, hence we need
to inquire into its cause as well. Another suggestion is that he was created by
several partial causes. This fails, though, since the concept of infinite
perfection is unified, so the cause of it must be unified. Finally, he addresses
the suggestion that he was caused by his parents. Although his parents may be
the cause of his body, they are not the cause of his thinking existence insofar
as he has an idea of infinite perfection. Descartes concludes that God must be
the cause of him, and that God innately implanted the idea of infinite
perfection in him.
This dependence of Descartes' existence upon God's provides yet another,
reinforcing plank of the cosmological argument for God's existence. In general,
the cosmological argument always begins with a contingent something, and then
reasons towards a necessary being. Had Descartes been able to account for his
own (initial and continued) existence in some other way (perhaps by claim that
he, himself, was a necessary being), then the cosmological argument could never
have really taken off. But more than that: he has provided an account of the
possibilities of his own creation and conservation in existence that weaves the
idea of God into the nature of that existence. Descartes now defines himself, at
least in part, as the being that has the idea of infinite perfection. His
mind could easily wander from an argument that begins with an idea of God, if
that were just one idea among others (earlier in Mediation Three Descartes had
lumped all ideas together in just that way). However, the fact that he exists as
a being that has within it an idea of an infinite perfection serves as a
comtinually present and unmistakable mark of his being contingent and thus
dependent upon a really existent God. It is significant, then, that Descartes
should end Meditation Three by withdrawing into comtemplation of God. (This
notion of radical dependence is also obviously of the highest importance
theologically.)
Descartes closes Meditation Three arguing that God is not a deceiver since
deception is an imperfection, and God is infinite perfection. This solves the
problems raised at the beginning of this section. Descartes also claims that, as
God's creation, it is highly plausible that God made him in his 'image', and
that he understands God by those same acts of inner perception by which he
understands himself. The argument is very compressed here. Among other things,
these three points together will mean that Descartes can rely upon such mental
abilities as intellectual perception and memory. Since, had his creator given
Descartes a systematically flawed intellectual perception, Descartes would be
unable to grasp the idea of God and pursue its implications, and that would be
equivalent to God's deceiving him. If intellectual perception is made in the
image of God's perfetion, however, then the whole method of clear and distinct
ideas can be relied upon. The general reliability of memory is important, too.
We already saw Descartes expressing doubts about his arguments once his mind
wandered. Descartes seems to be suggesting that the argument demonstrating God's
existence, together with my dependence upon God for existence, only needs to be
worked through once - from that moment on, we can progress onto other topics,
confident of truths that are built upon without continually being
perceived clearly and distinctly. However, Descartes only gestures towards these
ideas at the end of Meditation Three; they become extremely important later (see
below).
Towards the beginning of this encyclopaedia entry, we argued that Descartes'
strongly advocated a distinction between faith and reason. This meant, for
example, that Descartes could feel free to doubt the particular theological and
philosophical perspectives of the Church, while remaining a Catholic. On many
occasions, moreover, Descartes makes a more precise distinction: between those
aspects of theology that are available to 'natural reason' - i.e. to the
reasoning powers that belong to the human mind working on its own - and those
that are objects of faith. (Descartes' fascinating account of transubstantiation
being a good example of the former; the nature of the Holy Trinity being
Descartes' most common example of the latter.) Faith in turn requires revelation
and Grace. (See especially two letters to Mersenne, dated October 28th 1640
[III, 155] and March 1642 [III, 211].) Descartes however does believe that the
results of natural reason, properly employed, can not be at odds with the
theology of faith. Meditation 4
At the close of the Third Meditation, Descartes has arrived at all of the
fundamental principles he needs in his quest for truth: (1) he exists thinking
(a foundational fact which is indubitable), (2) God exists and is not a
deceiver, and (3) clarity and distinctness are reliable indicators of truth.
Descartes' goal is to show that knowledge is possible and scepticism thus
defeated; an important subordinate end in all this is to prove that we can rely
on our senses to at least some degree, and that their prima facie claims
concerning the external world can be verified after all. He believes he now has
the tools in place to achieve these ends. Meditations 4 and 5 do not contribute
directly to these goals, however. Meditation IV concerns the source of human
error. For it might be objected to Descartes' arguments thus far that, if in any
sense God is responsible for our mistakes, either directly or indirectly, then
this obviously would throw into doubt the newly arrived at claim that God is not
a deceiver. Thus, Descartes needs to find an account of error that avoids two
traps: (1) the trap of accusing God of deceiving us; and (2) the trap of making
certain knowledge seem impossible.
Descartes' concept of 'error' is broad, referring to any mistaken judgment
whatever. This includes assertions, predictions, ethical judgments, or judgments
leading to an action. Descartes begins his quest for the origin of error by
considering several theories which he ultimately rejects. He first considers
whether God could be the cause of his error directly. He quickly rejects this,
though, since God is not a deceiver - this is essentially the same move as in
Meditation 1, when the malignant demon is put in place of God's direct
deception. He next considers the possibility that human error results from his
faculty of judgment. That is, the human ability for form judgements is not
perfect. This makes sense since he sees himself as finite, existing on a middle
rung of the great chain of being between God and nothing. Thus, the possibility
of error would seem to be a defect that we can blame on our faculty of judgment.
However, it unsatisfactory to say that human error results from his faculty of
judgment since a perfect God would not place an imperfect faculty in him.
Descartes is puzzled that God could have made him such that he would never err,
yet he clearly does err, and he suggests that maybe he can never know God's
purpose in allowing us to err, since the wisdom of God is above human intellect.
However, he concludes that we should examine God's purpose in creation as a
whole, not just his purpose in creating me personally in a manner that involves
error. In other words, there is no contradiction in supposing that God's broad
purpose, though a purpose suiting an infinitely perfect being, includes the
narrower detail of our possessing a faculty of judgement that can fall into
error.
Descartes next considers the specific faculties involved when we make
mistakes: the understanding and the will. The distinction here between
understanding and will occurs on the back of the earlier distinction between
ideas as mere modes of thought, and judgement. He can find no reason to hold
either of these faculties individually responsible for error. Our reason cannot
be faulted since, first of all, the ideas we do have cannot be considered
formally false (as we saw above in Meditation 3). And, secondly, concerning the
ideas we do not have, this lack cannot be counted a positive defect of
the intellect (a flaw), but merely a characterisation of its finitude. (The fact
that my stapler cannot also write the documents that I staple together would not
normally be considered a flaw in the device, merely a limitation of it.) I
cannot complain of God that He did not give me a greater faculty of knowledge,
as if I were somehow entitled to it! The intellect within its limits has no
inherent defect, but it does have those limits. The faculty of the will itself
does not produce error since the will is a perfect faculty (I can will anything)
- indeed, my will is as perfect as God's (God's is only greater in terms of
power, knowledge, and the objects He can affect). Descartes briefly discusses
the free nature of our will. Even when strong motives stemming from the clear
and distinct apprehension of things by our intellect incline us toward one
direction, we choose all the more freely in that direction. Freedom is at its
lowest when no motive in the intellect moves me more in one direction than in
another. This is because, as we shall see, it is the perfection and role of will
to follow our knowledge, rather than to lead it.
Descartes considers a final view that error results when we extend our will
beyond our knowledge. This, he believes, is the true explanation. According to
Descartes, our will often becomes indifferent (or lazy) and accidentally extends
beyond the bounds of our knowledge, asserting judgements where the understanding
of the ideas is insufficient. He stresses that we should abstain from willing
when we have insufficient knowledge. As an example, he explains that at this
stage in his investigation he doesn't know whether his essential qualities
include mind, body, or both. Hence, he abstains from any wilful judgment on this
issue. In this and similar cases, he believes that proper use of freedom
requires us to abstain from wilful judgment. Suppose, though, that, by chance,
we stumble upon some truth beyond the scope of our knowledge. For Descartes, it
would still be improper to use the will in this manner since I know clearly and
distinctly that full knowledge ought to precede volition. (For a further
discussion by Descartes of these ideas concerning will and freedom, see the
letters to Mesland of May 2nd, 1644 (III, 233ff), and February 9th, 1645 (III,
244ff).)
Descartes next argues that even though God created us, God is not responsible
for errors that we make. He considers several possible criticisms against God's
role. One might first criticize God for giving us limited knowledge. However, as
we saw above, finitude is my essence, and this involves limited knowledge (God
was not required to make me infinite). Second, one might criticize God for
allowing us to extend our will beyond our knowledge. In reply, Descartes argues
that God merely allows us to make erroneous wilful judgments, but does not cause
us to make them. Third, one might also criticize God for not more actively
preventing me from erring. For example, God could have given me clear and
distinct perception of everything I would ever need to know. Alternatively, God
could have impressed more firmly on my memory the importance of not extending my
will beyond my knowledge. However, although this would make me more perfect,
when I view the goodness of the whole universe, God may have some need for me to
be a less perfect being. Again, we return to the argument that my limited view
of the purpose of God's creation does not authorise me to judge whether any
particular aspect of it ought to have been more perfect. Descartes argues
that we don't need God to impress more firmly on our memories the importance of
restraining the will. By developing the right habits, we can do this ourselves.
Through practice, I can develop such habits when I remember previous
circumstances in which I over-extended my will.
Descartes has here expanded on the notion of God not being a deceiver. The
concept of deception has at least two elements: first, it would be a deception
if God systematically made the prima facie source of ideas appear other
than it in fact was. (I.e., some ideas appear to come from the external world,
but this could be a deceptive appearance.) Accordingly, in Meditations 1 and 3,
God's quality of non-deception was commissive in that a perfect God could
not commit any act that would deceive. Second, it would be a deception if God
somehow made it systematically impossible (rather than just difficult)
for me to recognise deception of the first type - that is, if I were prevented
from having or using the intellectual tools (such as clarity and distinctness)
that I would need in order to discover deceptions of the first type. Thus, here
in Meditation 4 (and again in Meditation 6) Descartes argues that a perfect God
cannot omit any preventative measures that would be required for Descartes to
understand the truth. God's non-deception, then, is also omissive. This
commissive/omissive distinction is similar to the notion of sins of commission
(such as the direct stabbing of an innocent person) and sins of omission (such
as refusing to rescue a person from drowning). Descartes maintains, then, that a
non-deceptive God can perform neither deceptions of commission, nor deceptions
of omission. Much of Meditation 4, then, is trying to understand human error
such that it cannot be seen as a deception by omission on the part of the
creator of the human intellect. Incidentally, such considerations also remove
the hypothesis of the malignant demon who 'stood in' for God in Meditations 1
and 2. And that in turn explains why Descartes does not feel the need to return
to that hypothesis from Meditation 4 onwards. Meditation 5
In the Fifth Meditation, Descartes presents another argument for God's
existence. Like the argument in Meditation 3, Descartes' argument here does not
appeal to sensory information (such as natural design). Instead, it too is based
on the content of his thoughts. However, it does not hinge on the concept of
sufficient reason, as in Meditation 3. The proof in this Meditation broadly
follows Anselm's ontological argument; though in the first Replies, Descartes
states why his version is not subject to the objections raised against Anselm by
Aquinas (II, 82ff).
He begins Meditation Five noting that he can imagine an array of two and
three dimensional shapes. Some of these, like triangles, portray clear and
distinct attributes that necessarily belong to them, and do so irrespective of
whether we have sensory knowledge of the objects of these ideas, or even whether
these ideas have existent objects at all. That is to say, the intuitive
inspection alone of some ideas yields the absolutely certain predication of
attributes of them. Further, I cannot but assent to the truth of these
properties, at least in the act of intuitive inspection, since it is the nature
of my will and judgement to follow the understanding where the understanding has
such clear and distinct insight.
It is no accident that Descartes is using as his examples here issues of
quantity of extension in geometrical figures; this is a further instance of his
consistent privileging of primary over secondary qualities on the grounds of the
former's clarity and distinctness. Although the actual argument is missing,
Descartes signals his intention in the title to the fifth Meditation: 'The
Essence of Material Things.' The aim, ultimately, is to prove that extension and
extension alone is the essential property of all material things. This will be
true even if material objects turn out not to even exist! (Please see the
discussion of Meditation 6, below.)
In the same way as the analysis of the idea of the triangle, from the mere
idea of God (that is, a supremely perfect being) we can arrive at necessary
attributes that belong to him. Put more precisely, Descartes' proof of God is
this: My confidence in the existence of God is therefore just as high as the
confidence I have in the truths of mathematics. Descartes' wording here implies
that this confidence, though high, is less than perfect.
Descartes next anticipates three possible objections to his argument. A first
objection to Descartes' proof is that God can be thought of as not existing.
That is, we can separate his existence from his essential attributes; after all,
this separation is certainly possible with any other idea I examine. Since,
according to the imagined critic, we can conceive of God as not existing, then
existence is not a necessary attribute of this idea. Descartes replies that we
cannot separate God's existence from his essential attributes when we carefully
consider this idea. With other ideas, we can separate out the existence from the
other attributes only because the ideas are not of a perfect being. In the Fifth
Replies (II, 262-4; and again in Principles part one, §14-5, I, 197-8),
Descartes elaborates on this by distinguishing (conventionally enough) between
merely possible, and necessary existence. There he claims that possible
existence is not to be considered a property of an idea, since all ideas have
that property by virtue of being ideas; that is, we normally consider ideas 'as
if' their objects existed. However, necessary existence is different, and is a
positive property. With God, then, the inclusion of existence among the
necessary attributes is just as clear as the idea of a valley being included in
the idea of a mountain.
A second objection to Descartes' proof commences with just that famous
example: even though a necessary attribute of a mountain is that it be adjacent
to a valley, it doesn't follow that any mountains or valleys exist. In the same
way, even though the concept of supremely perfect being necessarily possesses
certain attributes, it doesn't follow that this being exists. It only entails
that should a God exist, His existence would be necessary. Descartes replies
that this misses the analogy, and falls to his reply to the first objection.
With ordinary ideas, to be sure, existence is never necessary - but other
properties may be, and that is where the analogy lies.
Descartes' third self-criticism is that it is not necessary for me to think
about or suppose the idea of God at all, but once I do, then existence is seen
to be necessary. But how (the objection continues) is this different from it not
being necessary for me to suppose some proposition that is false, but once I do
then some other false proposition will follow necessarily? Descartes' reply is
easy enough: my examination of the idea of God for what clearly and distinctly
belongs to it is not necessary to be sure, but is also not false. Not everything
I think about contingently is thereby false!
Descartes argues that absolute knowledge of anything, including geometry,
depends on a prior knowledge of God. (Descartes repeats the argument here about
the innateness of the idea of God, which was first made in Meditation 3.)
Suppose we are analyzing an elaborate geometrical proof. While all of the ideas
are fresh in our minds, we can see that the proof is sound. However, as time
passes, the details of the proof are no longer in our minds, and we might then
doubt the soundness of our proof. But, even if we forget the details of a proof,
we can still rely on our established conclusion insofar as each step was
perceived clearly and distinctly. Since God is not a deceiver, then we can trust
that all we perceive clearly and distinctly is necessarily true. Unlike
elaborate proofs in geometry, Descartes argues that it is quite easy to
understand that existence is a necessary attribute of a supremely perfect being.
The relative - indeed perhaps the ultimate - simplicity of the ontological
argument seems to bypass the need for memory in comprehending proofs. This helps
us to understand why Descartes felt the need, in Meditation 5, to supply a
second proof for God's existence.
It follows, Descartes reiterates, that the certainty and truth of every
science depends on knowledge of the true God. This famously poses a problem for
Descartes, however: if it is clear and distinct perception or intuition that
allows him to prove the existence of God, and it is the existence of God as a
perfect being that guarantees the validity of the criteria of clarity and
distinctness, then is not Descartes guilty of arguing in a circle? One of the
writers of the Second set of Objections, as well as Arnauld who wrote the
Fourth, noticed this apparent problem(II, 89; II, 150). In both these instances,
Descartes reply involves restressing the above point about the distinction
between present clarity and distinctness, and remembered clarity
and distinctness. That is to say, it is Descartes' intellect itself that is
capable, in a given present instance, of attaining to and being certain of that
which is apprehended clearly and distinctly. Where present clarity and
distinctness is attainable, there can be no doubt, even before the proof for the
existence of a non-deceiving deity. (However, it might appear that Descartes
contradicts this approach in the discussion of mathematics at the beginning of
Meditation 3 (II, 25).) However, once the mind passes on to a new issue it must
rely upon its memory of having previously been assured of clarity and
distinctness. Descartes reasons that God's perfect and nondeceiving nature would
be placed in jeopardy if He had created the human intellect with a such a defect
that it could not in general rely upon past convictions, that the intellect did
not 'tend towards truth'. (Of course, passing on to a new issue may mean
proceeding to the next step of a demonstrative argument, like the one proving
God's existence. Descartes has to assert, as he does for example in his reply to
Arnauld's objection, that one can 'attend' to at least a simple argument as a
whole. See also Descartes' peculiar account of the 'sweep of thought' in the
seventh of the Rules for the Direction of the Mind (I, 25).) Meditation 6
Review; and the 'Probable' Argument from Imagination
At this point in the Meditations, Descartes has obtained certainty
about a variety of topics: his existence, his essence, the causal principle,
God's existence, that God made him, that God is not a deceiver, that clarity and
distinctness are indicators of truth, that he has a free will, the source of
error, and that God is the source of confidence in elaborate proofs. Descartes
sets two aims in Meditation 6: first, to show the existence of material objects,
and, second, to show that mind is distinct from body.
Recalling the distinction made earlier between primary objects of perception
(objects of mathematics) and secondary objects of perception (apparent objects
formed from observer-dependent sensory properties), Descartes investigates
whether material objects exist by asking two questions: (1) do primary objects
exist? and (2) do secondary objects exist? In answering the first question,
Descartes draws on a distinction between imagining primary objects and
conceiving of primary objects. He notes that he conceives of primary objects
(such as triangles) clearly and distinctly, but this in no way means that such
objects actually exist. It only means that they might exist since the
idea contains no contradiction. (See the discussion of possible existence in the
treatment of Meditation 5 above.) In addition to conceiving of primary objects,
though, Descartes says that he can imagine many primary objects as well. We can,
for example, intellectually conceive of a chiliagon (a thousand sided figure)
although we cannot imagine one (i.e., visually picture one in our minds). At
best, we would imagine a sort of vaguely many-sided object. Moreover, the mental
acts involved in conceiving and in imagining are recognisably different kinds of
mental effort. These analyses show, Descartes claims, that conceiving and
imagining are fundamentally different. This leads him to a further claim: that,
while conception is a necessary attribute of humans, imagination is not. Lacking
imagination, I would still be 'me' as a thinking entity. Thus, Descartes
reasons, the imagination seems to have something to do with my body which, since
I can even doubt its existence, is also not an essential part of me and is
obviously bound up with the kind of things (extended and material objects) the
imagination represents. In imagination, he writes, the mind 'turns towards the
body' (II, 51). However, it would follow from this that if the mind can imagine,
then there must exist body. Descartes believes this line of reasoning is only
probable, however, since he cannot rule out another (as yet unthought of) way of
explaining the nature of imagining. Since we can conceive of primary objects,
then such objects possibly exist. Since we can also imagine these
objects, then such objects probably exist, yet we cannot say for sure
whether they do exist.
Failing to attain certainty about the existence of primary external objects,
Descartes turns his attention to secondary external objects. (Of course, we know
from our previous discussions of the primary/secondary quality distinction in
Descartes that we are doomed from the start in trying to show that secondary
objects exist.) Since his notion of secondary objects rests on his faculty of
secondary perception (which still might only be an illusion) he needs to explore
this faculty. He does this by giving a summary of the first three Meditations,
noting what conclusions he has already arrived at about secondary perception. He
recalls first that he had a naive confidence in his senses (secondary
perception) by which he perceived the different parts of his body, different
emotional and physiological appetites, and various secondary qualities in
objects such as heat and color. He next recalls how he gradually lost all
confidence in the reliability of these secondary perceptions. There were three
steps to this doubting process. First, we are misguided by optical illusions.
Second, our perceptions may be dream states, and, third, God (or some other
being with the requisite powers) might be deceiving us. He recalls that external
sensations seem to arise from a source outside of himself, since such sensations
don't depend on his will. However, he might have a faculty that is the source of
seemingly external sensations and not know it. On the
Distinction Between Mind and Body
Descartes is now ready to present his argument demonstrating the existence of
bodies and the external world in general. The first part of the argument
occupies only a paragraph in Meditation 6, but is considerably expanded upon in
the Principles of Philosophy. It is intended to demonstrate that mind and
body are really distinct substances.
Descartes recalls how he attained certainty that God would not deceive him
about his clear and distinct ideas. One such idea concerns his identity as a
thinking thing, and the hypothesis that thinking is his only essential
attribute. This issue first surfaces at the 'I think, I am' stage of Descartes'
thought (e.g. Meditation 2). Recall Descartes' argument that whatever doubt I
may be able to maintain, I cannot doubt that I am doubting - that I exist as
doubting and, in general, thinking. Descartes then asks 'who' is this thinking
thing. That is to say, what is essential to it - as opposed to a property that
it happens to have, but doesn't need to have. As we saw, he moves towards a
conception of himself as essentially a thinking thing, that that is his
whole being. However, he then writes,
The only property I know that I have is thinking. But in Meditation 6,
he states more strongly that thinking is the only quality that the soul
possesses. The former is an epistemological claim, and the latter is an
ontological claim. With respect to this point in the Discourse,
Descartes' critics pointed out that the second claim can not be inferred from
the first. Thus his care here; and additional argument will be forthcoming in
Meditation 6. (In the 'Preface' to the Meditations, he implicitly claims
that his intention in the Discourse, was to merely make the
epistemological claim (II, 7).)
So, then, is thinking the sole essential property of me - or rather might the
body have the property of thought, or thinking the property of extension? (Note
that it is in their answers to this issue that Spinoza differs most famously
from Descartes.) Descartes is not yet in a position to be able to decide this
issue with absolute certainty. Descartes can, however, demonstrate that
the one property that is essential to all 'external' objects is extension: that
is, that they have size, shape and motion. All other properties - colour, smell,
even weight - all can be peeled away as inessential, leaving only extension (See
Principles, part 2, §4, I, 224.). We should make two observations here:
First, this move by Descartes has extraordinarily important consequences for
physics. It means that all of the secondary qualities are to be traced back to,
and effectively reduced to, primary qualities. Physics has only one real quality
to worry about: extension, broadly speaking (Principles, part two, §23, I
232-3). Moreover, extension can be exhaustively understood in mathematical
terms. Therefore, the whole of the physical world is essentially
mathematical in character. This is a titanic jump from Aristotle, and places
Descartes along with Galileo as one of the early founders of modern physics.
Second, it is important to see this type of analysis as a basic part of
Descartes' method. The central idea is that a clear and distinct conception
allows one to grasp a thing's properties as either essential or accidental
(non-essential). This ability follows from distinctness - for, remember,
distinctness is defined as being able to fully describe the differences between
one thing and any other.
An accidental property is one that does not indicate a real distinction
between substances. For example, if I had a clear and distinct idea of
Camelus bactrianus as a species, then I would know that its distinction
from Camelus dromedarius, is not that it has a sore left front leg, or
that its name is Ginger. These are only distinctions between particular
individuals, and are entirely contingent with respect to the distinction between
species. Instead, I would know that the real distinction is that the former has
two humps rather than one. The problem with this kind of analysis - or one
problem at any rate - is that what is essential to my idea of something may not
be essential to the thing the idea is of. Descartes is analysing the properties
of our ideas. These ideas, as we have seen, have a certain objective reality -
they claim to be representations of things. But whether they are or not - and
even if they are, whether they are accurate representations of things - remains
to be decided. So, Descartes asks, is it obvious, from the fact that my clear
and distinct conception of mind has the sole attribute of thinking and that my
clear and distinct conception of body has the sole attribute of extension, that
mind and body are separate substances? No, Descartes states, it is not. The
first reservation being that while thinking is certainly one property of mind it
may not be its unique essence, and similarly with body and extension. And
secondly, perhaps, these attributes are the one and the same: they may only be
different modes of each other. Thus the problem in the quotation above.
What we are asking for, essentially, is 'what kind of distinction is the
distinction between extension and thought?' Descartes says that there are three
different types of distinctions (Principles, part one, §60-2, I, 213-5):
A defining (or, 'principal' (Principles, part one, §53, I, 210-1))
attribute is that attribute of a substance which distinguishes it from any other
type of substance, and thus without which that substance could not be conceived.
It is the defining or principal attribute that clear and distinct perception is
supposed to ascertain. Every substance has only one defining attribute. It may
have other 'common' attributes too - e.g. existence, duration, etc. - but these
do not distinguish one substance from another (see Principles, part one,
§62, I, 214-5). Suppose a substance A had more than one defining attribute. It
would be possible for there to be a substance B that had just one of these
attributes. In that case, the real distinction between A and B would turn on
only one defining attribute, contradicting the supposition. (But does this
guarantee that for every substance there is only one distinction of thought?
That is, that there is only one property without which the substance cannot be
clearly and distinctly thought?) Descartes argues, as we have seen, that
material substance has the defining attribute 'extension'. Mental substance has
the defining attribute 'thought'.
Then - again, as we have seen - the problem of the divine author of our Being
enters the equation. Descartes writes, at the end of Meditations 4,
The existence of God gives general validity to the 'clear and distinct' test;
that is, we can now claim that that which is clearly and distinctly true once
will always be true, will be maintained in its truth. (Recall this is Descartes'
reply to the charge of circular argumentation.) But more importantly here,
anything that is clearly and distinctly conceived must be considered possible -
that is, God could produce it, if He so chose. What that means here is
that anything which is clearly and distinctly seen to be separable from
something else, must be so in fact (a fertile proposition that one can even find
in Hume). For God certainly has the power to separate any two such things
without essentially altering them. For something to not be its own essence is a
contradiction, and everything is possible for God except contradictions -
although clearly He can make any substance exist or not exist, or create
something with a different essence. This allows Descartes to make the following
argument: In the Dedication to the Meditations, Descartes argues that one of the
two main objectives of the book is to prove the immortality of the soul.
Interestingly, Descartes scarcely addresses this issue in the
Meditations. Therein, his most complete discussion of the subject appears
in the 'Synopsis' to Meditation 2, along with his reasons for not pursuing the
topic further in the book itself (II, 9-10). He begins his discussion by
describing when the issue of immortality should be addressed in the order of his
investigation. One factor in establishing the immortality of the soul is showing
that the soul is composed of an indestructible and unalterable substance.
Although the material substance of the human body is in general indestructible,
the composition of the body is alterable. Thus, the body as such is not eternal.
The spiritual substance of the human mind in general is also indestructible. Of
course, our minds also change when we have different perceptions. Using
Aristotle's terminology, these changes are accidental, though, and not
essential. In a letter to Mersenne dated December 24th, 1640 (III, 163),
Descartes distinguishes between showing the absolute 'immortality' of the soul
(an impossible demonstration, Descartes says, for he there takes this to mean
that God cannot destroy it) and the simple fact that the soul's existence is
different from the body's. What is important about this is that Descartes
clearly feels enough has been said simply in saying that the soul is
ontologically distinct from the body, and is therefore not subject to alteration
and death in the same way. Clearly, the argument is not considerably different
from Plato's in the Phaedo. The
Existence of Extended Bodies; Space
Let us return to the reconstruction of Descartes' argument for the real
existence of extended things. So far we have only shown that extension is indeed
the principal quality of matter, and that mind and extended matter are different
substances. Descartes continues by explaining that we are designed with several
mental faculties which are responsible for various ways of thinking. He is most
concerned here with the passive faculty of perception, that is, the ability of
receiving and recognizing the ideas of sensible things. But we can only perceive
what is in some sense given actively, that is, from some source or cause. This
implies that there is an active source of these ideas, either inside or outside
of him. That is, if I passively (or non-wilfully) perceive a rock in front of
me, then there is some active source feeding me that perception. Descartes sees
only three possible explanations of that active source: the perceptions are
actively produced by either himself, God (or the malicious demon, though this
has already been ruled out), or external objects. He eliminates the first two
options and concludes that external objects are the active source of such
perceptions. The argument runs as follows: In summary, Descartes argues that humans are spirits that occupy a mechanical
body, made of extended substance, and that the essential attributes of humans
are exclusively attributes of the spirit (such as thinking, willing and
conceiving) which do not involve the body at all. Attributes, such as sense
perception, movement, and appetite require a body, are attributes of our body
and not of our spirit and, hence, do not comprise our essence. The set of
arguments just considered prove two important things that Descartes has been
after for some time: first, that mind and body are genuinely distinct
substances; second, that we can have indubitable confidence that extended bodies
do exist.
Extended bodies suggests the concept of space in general, although Descartes
did not give the subject prominence in the Meditations. But Descartes'
views, and others similar or opposing, became one of the 'hot' topics in
philosophy throughout the Seventeenth and Eighteenth Centuries. In
Principles, part two, §8-12 (I, 226-8), Descartes gives the following
argument: This argument itself has a long history, going back to Aristotle. The
difficulty was always the apparent impossibility of thinking of space as itself
a kind of thing, separable both from particular things, and from us as observers
of it. A similar issue was the subject of a famous debate between Leibniz and
Clarke (a follower of Newton) at the beginning of the 18th Century; moreover,
just this issue was terribly important in the genesis of Kant's groundbreaking
new philosophy at the end of the 18th Century. (Please see the entries on
Leibniz and Kant in this encyclopaedia.)
One of the immediate consequences of Descartes' account of space is that,
strictly speaking, a vacuum cannot exist (Principles, part two, §17-19,
I, 230). Another, is that space, considered now as the totality of extended
substance, is extended without limit - the universe is infinite (ibid, §21, I,
232). Finally, Descartes argues that his analysis of space means that there
cannot be a plurality of worlds or spheres, such as were typically posited in
the Greek and Medieval periods (ibid. §22, I, 232). Thus, the physics that
pertains on Earth also pertains everywhere else; the physics that pertains to
the present is the same as in the past, or future. A Galileo or a Newton can
study the motions of the stars and planets, with complete confidence, from their
parlours. The Relation Between Mind and Body; Innate Ideas;
Interaction
We must be careful when thinking about Descartes' famous dualism of mind and
body; that is, the thesis that mind and body are different, and thus ideally
separable, substances. In the Latin text of the Meditations, Descartes
uses different words for body in the general sense of extended entities, and for
body in the specific sense of his own (or any human's) arms, legs and torso.
Descartes argues that a distinct idea of my own mind does not include the ideas
of imagination, sensation, purposeful movement of body, appetites or most
emotions (Principles, part one, §48, I, 208-9). That is, had I none of
these things, I would continue to be the same self, although in a much
impoverished manner, and could still think (and that alone is my essence) in
other ways. All of the above involve some relation to the body.
But the reverse is not true: it is impossible to think of imagination or
sensation or purposeful movement without a mind. That is to say, the former are
of the body, but not merely of the body. Descartes writes, 'In imagining,
it [the mind] turns towards the body' (Meditations 6, II, 51). These things are
distinct from mind as possible modes are from a thing (e.g. as a cuboid shape is
from a body). On the other hand, mind cannot be thought without it thinking, at
least in the sense of pure thought - therefore thinking in the non-bodily sense
of 'pure' intellection (see Principles, part one, §32, I, 204) is an
essential mode. This distinction between merely possible and essential modes
provides an argument for the separability of pure mind from things of the body.
But, again, 'separability' does not mean 'separate' - the immediate and almost
overwhelming fact of our existence is the factual togetherness of mind and body.
Nevertheless, that which in the body produces sensations (i.e. the
nervous system and the organs of sense) is not even a possible mode of mind, for
we can think of it separately from mind. And similarly with all other features
of body and world. Rather than modes of mind, they must be modes of a completely
separate material substance, defined essentially in terms of extension. Thus,
the whole visible world is 'as if it were a machine in which there was nothing
at all to consider except the figures and motions of its parts'
(Principles, part four, §188, I, 279). There, Descartes is speaking of
cosmology, signalling a change to come in the discussion of bodily sensation.
And yet he continues to apply this metaphor in the sections that follow, in the
discussion of the 'motions' of 'nerves'. Thus, although experienced sensation is
not to be understood through body alone, the body considered on its own is the
object of a physical science (physiology).
However, our body as that which has purposeful movement (body as that which
belongs to me as a conjoined being) is not merely such a machine. The soul is
not a 'ghost in the machine' for Descartes, as anti-Cartesians have sometimes
alleged. Rather, from the point of view of the self, the presence of the soul
'animates' the whole body, making it different from other matter. Thus, the body
is a different kind of entity considered objectively from when it is considered
as mine. The mind and body are 'separable' in principle, but are in fact in a
'close and intimate union ' (Principles, part one, §48, I, 208-9). So
intimately, in fact, that huge parts of our everyday mental life are dependent
upon the body (indeed, as we have seen, Descartes uses the mere existence of the
imagination as a 'probable' proof for the existence of an external world at the
beginning of Meditations 6). So intimately, in addition, that the body has to be
considered a different kind of extended entity from the point of view of the
self. That is to say, the ideas we have of the body and mind in union are
different from, and irreducible to, the ideas we have of either extended matter,
or of thinking substance. ('Correspondence with Elisabeth', letter of May 21st,
1643 and again on June 28th; respectively: III, 217ff; III, 226ff)
Descartes' understanding of human bodies contrasts with his account of
animals. Descartes believed that, on earth, only humans have a dual spirit/body
nature. Non-human animals have only bodies and are essentially automata or
biological robots which behave according to their internal biological/mechanical
makeup. Thus, they do not think, even though they behave in ways which we might
mistakenly take to indicate conscious thought. Descartes' view was patently
rejected by many of his contemporaries. In his article on Rorarius in the
Historical and Critical Dictionary (1692), Bayle presents a long list of
criticisms against Descartes' theory. Even today Descartes' view is the object
of ridicule by animal rights advocates. Descartes' reasoning is presented in two
letters to Henry More (III, 365-6, 374). He argues that there are two sources of
motion in organisms. The first is mechanical and bodily and involves the
physiological mechanism of animal spirits. The second is mind or soul which is
incorporeal. Descartes believes that the mental cause of motion does not apply
to animals, and that all of their behavior can be explained by mechanical and
bodily events. The common reason for holding that animals think is that they
have sensory organs like humans. However, Descartes offers several reasons for
not ascribing thinking to animals. First, we acknowledge that lower animals
(such as bugs) move only by mechanics. Recognizing this makes it easier to see
why this is so of higher animals as well. Second, our own human bodies move
without thought, such as when we are in convulsions. Third, we can create
machines which move. His main argument, though, is that animals have no true
language. Interestingly, Descartes claims that he is not denying life or
sensation to animals, but only thought:
One of the famous consequences of Cartesian dualism is the necessity of
positing innate ideas. In accordance with the wax argument found at the end of
Meditation 2: if exterior objects are knowable with any clarity at all - and
they are, at least insofar as they are objects of the science of geometry - then
there must be innate ideas. Such ideas come not from the senses or the
imagination, but from the operation of the mind alone. Only such ideas have the
features of necessity or universality which are marks of such a science;
experiential ideas are, rather, contingent. Furthermore, ideas do not resemble
the objects they claim to represent. Because of this, we know that mind is
essentially a thinking substance and body essentially an extended substance;
that is, are essentially different. Therefore, no idea of extension can be
formed in the mind by the senses. It follows that for there to be any thought at
all of extended substance, the idea of extension must be innate - it must, that
is, belong originally to the mind. Similarly for all fundamental concepts
concerning the nature of things essentially different from pure thought, but
also all non-particular concepts (such as colour)! ('Comments on a Certain
Broadsheet', I, 303). Sense experiences - the affection of the mind by the brain
and ultimately by the body - are 'occasions' that stimulate the explicit arising
and positing of the innate idea as here or there applying to the world (ibid.).
The world 'impresses' itself upon our nervous system, but the nervous system
does not 'impress' itself upon the mind - rather, it stimulates the mind to
exhibit an idea of which it was already capable. Thus, Descartes insists that
the innate ideas are not separate from the faculty of thinking of the mind. In
the same sense, he writes, 'we say that generosity is 'innate' in certain
families' (I, 304). This stimulation by the occasion of experiences is
essential, for ideas are innate not 'actually', but potentially in the mind, as
dispositions, in so far as we might say the mind has innately not the idea so
much as the capacity to think the idea (I, 305).
This dualism presents a problem for Descartes insofar as an explanation is
needed as to how our minds and bodies interact in their separate realms. For
example, when my hand touches something hot, this sensation is registered in my
mind. Also, if my mind decides to remove my hand, this decision must be
transferred to my body, which results in motor activity. Thus, Descartes needs
an explanation of both sensory and motor communication between our spirit minds
and physical bodies. Unfortunately, the problem of the interaction between mind
and body is not solved just by their close 'union'. For they are still
essentially different kinds of things.
He offers such an explanation in Part One of The Passions of the Soul
(1649): the pineal gland in the brain is the gateway between the two realms (I,
340ff). He notes that there are two standard accounts of how the body and soul
are connected: through the heart, and through the whole brain. He rejects these
and suggests that the point of interaction is the pineal gland. This is because
it is a single gland in the center of the brain, which unites our doubled
sensory perceptions (e.g. two eyes). With sensory perception, information is
transferred to the pineal gland through animal spirits, blood, and nerves. With
motor commands, the gland is moved by the soul, and thrusts the animal spirits
towards the pores of the brain, and onto the nerves.
Problems of the type that Descartes has backed himself into here go by the
name of the 'third man problem'. The reference is to Aristotle, but actually
Plato first uses similar arguments in his strange dialogue Parmenides.
Expressed in Platonic terms, the argument runs as follows: Suppose that to
explain why a group of individuals are collectively called 'men', we posit the
existence of the 'Form' of man. Then, however, we have a new collective (the
original group plus the Form) needing a second Form that gives the identity of
that collective. And so on. This infinite regress is assumed a reductio ad
absurdum of the original supposition of the existence of Forms. In
Descartes' case, the problem is analogous. The problem is to understand how mind
and body interact. Suppose we explain the interaction by positing the existence
of a third thing that is 'between' mind and body. But then, we have three things
among which we must understand the interaction (how does mind interact with this
third thing? how does body?). We have to posit still further intermediaries, and
so on ad infinitum. Descartes' idea of the pineal gland as the site of
interaction must on principle fall to the same general problem. Thus, his
hypothesis is often taken as one of the most ludicrous moments in the history of
philosophy. However, to be fair, Descartes was probably using the pineal gland
as just the site (in the body) of interaction, not as an explanation. In the
same way, one might say that the church is the site of the interrelation between
humans and God - without that being an explanation of how that interrelation
happens. Moreover, Descartes himself also put forward several more intriguing
alternatives to the pineal gland as site. See in particular the analogy with
gravity where Descartes speaks of 'the whole of' mind in 'any one' of the parts
of the body (Sixth Replies, II, 298).
In fact, of course, Descartes was fully aware of the third man problem. In
the 'Correspondence with Elisabeth' as we have already noted, he asserts that
the fundamental notions by which we think the union of mind and body are
essentially different from the notions we have of mind or body separately.
There, he calls these 'primitive notions.' To say that these are primitive or
primary, also means that one will be unable to explain any such idea on the
basis of any of the others. Now, we know that extension is a primitive notion
(all other properties of the material world are reducible to it, and it itself
is really distinct from mind). Also and similarly, we know that thought is a
primitive notion. You cannot reduce thought to extension or extension to
thought. In that set of 'Correspondence', Descartes' gives two arguments for the
idea of union also being primitive. First: 'It does not seem to me that the
human mind is capable of forming a very distinct conception of both the
distinction between the soul and the body and their union' (III, 227) because it
involves a self-contradiction. Second, is that the interaction is known first
and foremost by the senses, 'That is why people who never philosophise and use
only their senses have no doubt that the soul moves the body, and that the body
acts on the soul' (III, 227). But sense perception in the full sense, as we saw
above, is precisely a product of the union itself - and therefore the primitive
notion of interaction it provides us is essentially unavailable to pure thought,
that is, to philosophy. It follows that, despite the fact that this union makes
perfect sense to ordinary experience, philosophy will never be able to grasp
this union or interaction.
... [M]ay it not perhaps be the case that these very things which
I am supposing to be nothing, because they are unknown to me, are in rality
identical with the 'I' of which I am aware? (Meditation 2, II 18)
... [B]ecause every clear and distinct conception is undoubtedly
something, and hence cannot come from nothing, but must necessarily have God
for its author. Its author, I say, is God, who is supremely perfect, and who
cannot be a deceiver on pain of contradiction; hence the perception [or
judgement] is undoubtedly true. (Meditation 4, II, 43)
For Descartes, (4) above is the crucial premise to his argument.
Why does he believe that perceptions are not implanted in him by God? The answer
is that, first, Descartes has no faculty by which he could know if such
perceptions are implanted by God. Second, he has a strong inclination to believe
that secondary perceptions are the result of secondary external objects. Third,
Descartes argues that it would be deception on God's part if God (a) permitted
Descartes to erroneously believe perceptions are caused by objects and (b) did
not give him a faculty to know that such notions are actually caused by God.
This parallels the distinction between commissive and omissive deception which
we discussed in the section on Meditation 4.
Please note that I am speaking of thought, and not of life or
sensation. I do not deny life to animals, since I regard it as consisting
simply in the heat of the heart; and I do not even deny sensation, in so far
as it depends upon a bodily organ. Thus my opinion is not so much cruel to
animals as indulgent to human beings - at least to those who are not given to
the superstitions of Pythagoras - since it absolves them from the suspicion of
crime when they eat or kill animals. (III, 366)