Delivered at the British Society for the History of Philosopy conference on Descartes’ Meditations, Reading, 3–5 September 1991

The full title of the first edition of Descartes’ Meditations runs as follows: Renati Des-Cartes, meditationes de prima philosophia, in qva Dei existentia et animae immortalitas demonstratur (‘René Descartes’ meditations on first philosophy, in which the existence of God and the immortality of the soul is demonstrated’). In this paper, I am mainly concerned with the single word ‘meditations’. However, four other issues are worth mentioning as a preliminary.

First, the grammar is quite horrible. The singular in qva is made to agree with the plural meditationes, and the two subjects of demonstration are given the singular verb demonstratur. No wonder the second edition corrects these to in qvibus and demonstrantur. One can only speculate whether the mistake was Descartes’ own, or the printer’s — perhaps the latter, in view of Descartes’ change of printer from Michel Soly to Louis Elzevir.

Second, and more seriously, the original title claims that the Meditations demonstrate the immortality of the soul. Now, a case could be made for saying that, if Descartes’ account of the nature of the soul is correct, then its immortality is much more comprehensible than on the then orthodox Christian-Aristotelian account. If, as the Aristotelians held, the soul is nothing other than the form of the body, then its immortality implies either the resurrection and subsequent immortality of the body; or the substitution of the material body by a spiritual body which is neither mind nor matter; or a miraculous suspension, not merely of the laws of nature, but of those of logic. In many ways, the conceptually most satisfactory version of Aristotelianism is the Averroist doctrine that only universal Reason is fully real and eternal, and that individual souls are reabsorbed into it on the death of the body. By contrast, Descartes’ Platonic dualism abolishes any reason to suppose that the cessation of bodily activities will have any effect whatever on the soul — indeed, his problem is always to explain how the one can ever influence the other.

But the question of the immortality of the soul is not discussed in the Meditations themselves. Interestingly, most of Descartes’ ‘synopsis’ of Meditation II is taken up with an apologia for not discussing the immortality of the soul, on the grounds that the proof depends on ‘an account of the whole of physics’ [n.1]. He then immediately provides a proof that the soul is naturally immortal, based on two premises (hardly ‘physics’, and hardly the ‘whole’ of it), namely that the soul is distinct from the body, and that substances naturally continue to exist unless annihilated by God. Perhaps the point about the proof requiring the whole of physics is that the soul is independent only if it is not needed as an essentially active component of the body — only if Descartes can complete the project of the Traité de l’homme of explaining all bodily behaviour in terms of mechanical reactions to external stimuli. Of course, from the fact that the body doesn’t need the soul, it doesn’t follow that the soul doesn’t need the body: but it as a typically Cartesian position that, if two entities have essentially different natures (here the essentially ‘active’ soul and the essentially ‘passive’ body), then they are ontologically independent of each other. As for the continued existence of substances, in Meditation III, [n.2] Descartes claims that his continued existence from one instant to the next requires a continuous act of re-creation by an external agent. The implication is that immortality is not after all ‘natural’, but permanently subject to the grace of God.

Again, the word immortalitas may just have been a misprint for immaterialitas, [n.3] and in the second edition Descartes may have changed the expression animae immortalitas (‘the immortality of the soul’) to animae humanae … corpore distinctio (‘the distinction between the human soul and the body’) in order to guard against a repetition of the typographical error.

This emendation also deals, at least in part, with a third defect in the original title, namely that it gave no hint of Descartes’ radical dichotomy between the human soul and everything else in nature. Other Platonist philosophers of the time postulated a hierarchy of beings, in which beings inferior to humans also had souls, and thereby manifested a dualism of spiritual and material aspects. By contrast, Descartes held that everything other than human beings was wholly material, and indeed that most human functions could be explained in wholly material terms. While we tend to see him as a spiritualist because he failed to ascribe everything to matter, his contemporaries tended to see him as a materialist, because he ascribed so little to spirit. Although he retained some of the traditional terminology — in particular the expression ‘animal spirits’ — he reduced these spirits to extremely small, but utterly material particles permeating the body. In the text of the Meditations, he rightly preferred the word mens (or ‘mind’) to words like anima or spiritus, since it denoted something peculiarly human. In this he prefigured modern philosophers’ squeamishness about the words ‘soul’, and ‘spirit’ (though the modern squeamishness has more to do with the ontological implications of the terms than with the distinction between humans and animals). Descartes would perhaps have been better advised to have used in his title the expression mentis. . . corpore distinctio (‘the distinction between the mind and the body’).

The fourth issue concerns the phrase prima philosophia, or ‘first philosophy’. To quote John Cottingham [n.4]:

Descartes’ remark to Mersenne is in fact rather odd. If the Meditations are not ‘confined to God and the soul’, why should he specify just these topics in the subtitle? Again, at least in scholastic circles, the terms ‘metaphysics’ and ‘first philosophy’ were generally used interchangeably, since ‘first philosophy’ was what Aristotle described himself as doing in his book subsequently called the ‘Metaphysics’; and both equally involved rational theology. Leibniz, for example, persistently referred to the Meditations as Descartes’ ‘metaphysical’ Meditations — as also to Part II of Hobbes’s De corpore: philosophia prima as on metaphysics. [n.5] The answer may be that Descartes and Hobbes, neither of whom was well versed in the niceties of scholasticism, both wanted to distance the new discipline they were creating from scholastic metaphysics. They opted for the vaguer term ‘philosophy’, which still embraced most of what we would now call ‘science’, but called it first philosophy in order to distinguish it from detailed scientific theorising. Nevertheless, Descartes (or his translator) hedged his bets in the French translation, giving it the title: Meditations metaphysiques . . . touchant la premiere philosophie (Paris, 1647). Either way, the fact that he felt it necessary to add the subtitle on God and the soul suggests that both the expressions ‘metaphysics’ and ‘first philosophy’ were beginning to lose their traditional association with rational theology. This brings me to the topic of the word ‘meditation’.

It seems beyond dispute, both that Descartes had an almost messianic ambition to replace the Aristotelian philosophy and science with his own, and that he had a well worked out marketing strategy. [n.6] In the event, he was remarkably successful in overturning the academic establishment, and his success may in large part have been due to his calculated approach. He had a product, and he sold it to a number of different markets.

From our present perspective, we have a canon of ‘great’ philosophers, whose works we ransack more-or-less indifferently for evidence of what they really believed, irrespective of their titles. Familiarity may have blinded us to the rhetorical differences between principles and dialogues, essays and treatises, enquiries and treatises, treatises and tractatuses, tractatuses and investigations, and so on. In Descartes’ case we are faced with the distinction between a discourse, a meditations, and a principles (as well as some treatises and essays peripheral to what we now count as philosophy). What is the significance of these titles?

Descartes identified three categories of reader he had to win over. The first, and in his day the most important, was what one might call the ‘lay’ market. It consisted of the educated French public outside the university and college system who had some actual or potential interest in new philosophical and scientific ideas. The educational establishment had already become marginalised by the renaissance, which was largely a non-university, and indeed an anti-university phenomenon. The polarisation between two rival intellectual cultures was accentuated by the scientific and mathematical revolution, which sprang almost entirely from the ranks of non-university intellectuals. Galileo the university professor was exceptional; Descartes the gentleman scholar with no university degree was typical of the new breed of philosopher-scientist.

Not only was the market a large one, but it included most of those with power, influence, and money — royalty, the nobility, state officials, and so on. They were far more likely than anyone in the universities to be interested in new ideas with practical implications, and they were in a far better position to provide patronage.

The title signalled the targeted audience in two ways. First, it was in French, which meant that it was not a book for academics, but for what we now call the ‘general reader’, some of whom might not even know Latin — for example the queens and princesses who became interested in Descartes’ philosophy. The second way was through the word ‘discourse’, which implied an easy and informal conversation about the method, rather than a didactic treatise expounding the method systematically. As Descartes himself wrote to Mersenne in February 1637:

The second category of readership was the world of academic philosophy — always understood that the term ‘philosophy’ included both ‘first philosophy’, or metaphysics, and physical science. For this he wrote a basic text in Latin, with the appropriate title Principles of Philosophy. But before publishing this work, he felt it necessary to address a third type of reader.

These were the theologians. Here Descartes’ motives were primarily defensive. It was not that he wanted to replace Aquinas in theology in the way that he did want to replace Aristotle in philosophy, but that he saw the theological interest as a threat to his plans. He was well aware that his views on God and the soul were at best highly unorthodox, and at worst completely heretical. His life was dominated by the fear of ending up like Galileo, from whom he had derived many of his ideas; and the superior Faculty of Theology had the power to block innovations in the Faculty of Arts at most universities. Theologians had to be persuaded that Descartes’ philosophy was not dangerous to religion. Typical of his attitude is his blatantly insincere remark at the very end of the Principles:

The Meditations advertised itself as a theological work, not merely by its references to God and the soul in the subtitle, and by the epistle dedicatory to the doctors of the Theology Faculty at the Sorbonne, but by the use of the very word ‘meditations’ in the title.

Then as now, and in Latin and French as well as in English, the word ‘meditation’ could simply mean ‘thinking deeply’. But when used as a count-noun in the plural, it would imply a series of mental activities of a special sort — in particular a religious or mystical exercise. In classical Latin, one of the senses of the word meditatio was an intellectual exercise; and in the context of medieval spirituality, it acquired a specifically religious connotation. For example, the 14th-century mystic Gérard Zerbolt de Zutphen [n.9] defined a meditation as a particular exercitium spirituale, or ‘spiritual exercise’ which presupposes a certain length of time. Similarly, in 1630, Descartes’ contemporary Eustachius a Sancto Paulo published his Spiritual Exercises . . . Augmented by Six Meditations. [n.10] So, were Descartes’ Meditations intended to be taken as spritual exercises?

The best-known spiritual exercises were those of St. Ignatius Loyola. He too saw no distinction between spiritual exercise and meditation. In his Exercitia spiritualia [n.11] he writes:

Since what little formal education Descartes had was at the Jesuit college of La Flèche, he would have been fully aware of this. And there are indeed close analogies between Loyola’s and Descartes’ programmes. To give just some examples: They both have the voice-over of the Master leading the secluded novice through a sequence of thoughts to be adopted as the latter’s own. As Loyola puts it (p.140):

Again, Loyola’s procedure starts with the via purgativa, or ridding the soul of its previous beliefs and attitudes, and proceeds to the via illuminativa, whereby the soul is filled with new certainties (p.150). Similarly, Descartes’ ‘antecedent’ scepticism, as Hume calls it (though it could equally well be described as ‘brain-washing’), is followed by a gradual illumination, culminating in a thoroughly Platonic adoration of God as the source of light at the end of Meditation III:

In some ways Descartes is less mystical than Loyola. The light which guides his thoughts is a natural light rather than a supernatural one; and the conscience he examines is not a moral conscience, but the new psychological concept of consciousness as that which distinguishes humans from animals (not that he finds a name for his new concept — but that is another story). [n.13]

In other ways Descartes was more mystical than Loyola: his six days of meditation (as contrasted with Loyola’s twenty weeks) reflect the six days of creation; and his constant repetition of the expressions ego existo and ego sum (though interestingly never cogito ergo sum in the Meditations) are evocative both of God’s mystical name ego sum as in Exodus III.14, and of the oriental mantra ‘om’. [n.14]

Was all this nothing more than a rhetorical device to appease the theologians? I think not, for two reasons. The first reason is that, although the religious content of the work is undoubtedly high by comparison with Descartes’ other writings, it would appeal to only one wing of the Church, and would seem dangerously heretical to the majority of theologians. For example, his proof of the existence of God in Meditation III involves the claim that his mind can somehow grasp the divine essence. Still worse, he comes very close to denying both the individuality of human minds (as he did of material substances), and the distinctness of his own mind from God — rather in the manner of recent heretics such as the Brothers of the Free Spirit, who believed that the illuminati achieved identity with God. [n.15] Much of the latter part of Meditation III is occupied with somewhat shaky arguments to convince himself that he is not God. The argument ‘I doubt, therefore I am’ turns into ‘I doubt, therefore I am not God.’ But the meditator doth protest too much, methinks.

The second reason for taking Descartes as sincere is that the mystical aspect of his thought is central to the foundations of his philosophical system. He rejected all other accounts of knowledge: that it is derived from reading books, from logic, from dialectic, from sense experience. For Descartes, the sole source of knowledge was the examination, if not of conscience, at least of consciousness. Like Plato before him, he saw the philosopher’s task as that of purging the mind of beliefs acquired through worldly existence, to pave the way for a pure intuition of the essences of things — Plato’s forms, or Descartes’ ‘simple natures’. And both philosophers had the problem of describing one’s state of mind when the goal had been achieved. As in other mystical traditions, the solution was to lead novices through the same stages as the master had already gone through, so that they would end up with the same intuition. In the Meditations, the word ‘I’, which occurs so frequently, is being offered to the reader to refer to him- or herself.

Nevertheless, something can be said about the nature of the mystical intuition. In particular, it involves the obliteration of distinctions between essence and existence, or the universal and the particular, and between subject and object. This is a theme common to most mystical traditions. What is unusual about Descartes is his project for returning from the beatific vision to a reinstatement of the old dualisms, albeit in a very different form. The turning-point in his meditational Odyssey is the point at which he switches from intuition to deduction — from the obliteration of dualisms to their reinstatement. It is hardly surprising that there should be difficulties in understanding the Meditations as a consistent whole, if there is in fact a discontinuity between two methodologies (broadly his distinction, derived from the Paduan school, between the analytic and the synthetic methods), and two philosophies (idealism and dualism). Disentangling the components of the two pairs will not result in a consistent philosophical system (unless one aspect is discounted as ‘insincere’), but it will provide an explanation for many cruces of interpretation. I shall therefore now consider some of the implications of the above analysis for the principal topics of the Meditations — the self, God, matter, and the relations between these three.

If there is any sense at all to seeing the Meditations as initially a mystical exercise, there can be no question but that the cogito is an intuition rather than a deduction. The occasional passages in which Descartes asserts the opposite must be dismissed as part of his project for dressing up his philosophy in a form acceptable to the schools, whereby particular conclusions are logically deduced from general premises.

In the cogito, there is a conflation of three distinguishable intuitions: (1) Descartes’ own individual existence; (2) his essence as a thinking being, and (3) his substantiality as a thinking being. Most commentators have interpreted this conflation as a naive error on Descartes’ part. Error it may have been; but if I am right, it was not naive — Descartes knew perfectly well what he was doing. He was deliberately refusing to accept any distinction between his individual existence and universal Reason or Thought, or between Reason/Thought as an attribute, and as an underlying substance. To criticise him for failing to distinguish between ‘there is a thought now’ and ‘I, Descartes, exist as an individual thinking substance’ is to miss the point entirely.

Let us take first the essence/substance distinction. Whatever we may say about the special nature of the Meditations, the absence of any real distinction between essence and substance is a constant feature of Descartes’ philosophy — and in many ways one of its merits. Other philosophers have got themselves into a terrible mess trying to explain what substance is, if it is something other than an attribute capable of being comprehended by the human mind; or how there can be different kinds of substance, if they are distinguishable only by attributes distinct from substance itself; or what the relation is between substance and attribute. For Descartes, there is no real distinction between substance and attribute. Apart from God, the only truly self-subsistent being, they are merely different ways of conceptualising the same entity — as (relatively) self-subsistent, and as a universal attribute, particularised through individual modes or accidents. [n.16] In the case of Reason/Thought, a particular instance of the universal will be a particular piece of reasoning or a particular thought — nicely straddling the distinction between cogito ergo sum as an instance of reasoning, and ego cogito, ego sum as an instance of intuitive thought. Either way, they are modes, or ways of being, of the substance/attribute. The substance/attribute can exist only through some mode or other, just as for an object to be coloured it must have some colour or other. But the mode can exist only as the mode of an attribute, just as an object cannot have a particular colour without being an instance of colour in general. For Descartes, the relation between substance and accident is not that of a mysterious underprop mysteriously supporting accidents, but the logical relationship between a determinable and its determinate instances.

So, in the cogito, there is no distinction between the intuition of Reason/Thought as essence and as substance. But what about the particular and the universal? First a linguistic point. In the Latin of the Meditations, Descartes carefully prefers the ordinary-language word res (‘thing’) to the scholastic technical term substantia (‘substance’). In Latin, there are no definite or indefinite articles, and there is no distinction between ‘mass-nouns’ and ‘count-nouns’. In English, there is a relatively sharp distinction between words which normally take an article (e.g. ‘cigarette’); those which normally do not (e.g. ‘tobacco’); and those which are used in different senses depending on when they take an article or not (e.g. ‘stone’). Unfortunately, the word ‘thing’, the natural translation of res, is a count-noun only; whereas ‘substance’ can be either a count-noun or a mass-noun. When Descartes says he is res cogitans, the obvious translation is ‘a thinking thing’ But if we use the word ‘substance’, which has become naturalised in modern every-day English, res cogitans becomes ‘thinking substance’. The mass-noun/count-noun ambiguity cannot be preserved in an English translation, and the translator has to decide whether Descartes’ intuition is to be presented as of the existence of thinking substance in general, or of his own individual existence as distinct from other thinking substances.

Interpreting the soul as a universal fits perfectly with a Platonic interpretation of Descartes’ epistemology. For Plato, like is known by like, and the soul is akin to a universal. It can attain true knowledge of universals, but at best mere belief of the shadowy world of particulars. Descartes also confines true knowledge to knowledge of universals; and in view of his obvious Platonism, it is at least plausible to argue back to an interpretation of Descartes according to which he believes that universals are known by universal Reason, and particulars merely affect the particular, bodily senses.

So far I have played along with the accepted idea that Descartes starts by stripping away presuppositions, and then reinstates them, even if subject to some modification. In the case of the soul, I have argued that what he finds after stripping away the presuppositions is a universal, in which there is no distinction between principal attribute and substance, or between individual existence and essence. It is clear that he never reinstates the distinction between principal attribute and substance; but what about that between individual existence and essence?

The Meditations give a strong impression of Descartes’ individuality through his constant references to himself, his particular circumstances, and his own body. The impression is reinforced by Descartes’ excessive and idiosyncratic use of the word ego: normal Latin would be cogito, existo, sum, not ego cogito, ego existo, ego sum. Again, one of the earlier stages in his brain-washing process is to doubt whether other human bodies have minds. It is therefore tempting to see him as contemplating, and subsequently trying to escape from, an early version of 20th-century solipsism. But this would turn the position on its head. What Descartes doubts is the reality of anything which could serve to distinguish one mind from another, and he never gives any arguments to show that there are other finite minds distinct from his own. By the end of the sixth Meditation, there is an argument that there exists a separate world of matter. But the world of matter is homogeneous, and there is no argument that the world of Reason/Thought is any less homogeneous than that of matter. The implication is that Descartes himself is nothing other than a mode of infinite thought mysteriously conjoined with a mode of infinite matter. Since he never contemplated the possibility that his particular existence was unique, he had no need to argue for ‘the existence of other minds.’ If he was negligent at all, his negligence consisted in a failure to argue that there was more than one point of mysterious contact between thought and problematically existent matter.

The coincidence of essence and existence in thought has two further corollaries. First, if cogito ergo sum is a valid argument, then sum ergo cogito should also be a valid argument. It is no accident that Descartes believed that the soul always thinks, or that, if the being of the soul is to think, it cannot be without thinking. To the obvious objection that we have no thoughts when we are unconscious, he replies that when we are unconscious we have no memory of one thought to the next.

A second and more important corollary is that only a thinking being can exist. This would be closely parallel to Berkeley’s esse est percipere aut percipi, where that whose existence is percipi is merely a mode of that whose existence is percipere. On any interpretation of Descartes, the existence of matter is at best problematic, since its existence is separate from its essence. On the above idealist interpretation, the material world reinstated in the sixth Meditation should not be fully real. I shall come back to this shortly.

A separate question concerning the mind is that of the obliteration of the distinction between subject and object in the cogito. An essential part of Hume’s critique of Descartes was his insistence that there must be a dualism between the self as subject, and ideas in the mind as objects of consciousness. Is there any sign that Descartes’ reinstatement of dualistic thinking brings back a distinction between the subject and the object of thought? Again, no. It remains a tenet of Cartesian philosophy that the self knows itself without any intermediary.

As for God, I have already claimed that Descartes achieves a vision in which his mind is filled with the infinite essence of God. His problem is then to distance God’s existence from his own being, so that he has a basis in external reality on which to build up an account of a real world distinct from himself. His account of the real world depends entirely on the claim that all his clear and distinct ideas are God-given, and that since God is not a deceiver, these ideas (but only these ideas) correspond to reality. It is a commonplace of Cartesian criticism to point out that he cannot without circularity use the criterion of clear and distinct ideas to establish the first stages of the argument — his own existence, the separate existence of God, and the fact that God is not a deceiver. But he doesn’t. At the beginning of Meditation III, he says he seems to be able to take it as a general rule that everything he clearly and distinctly perceives is true; but he then goes on to make it clear that he cannot do so until he has established the existence of a non-deceiving God. In fact he is very careful not to appeal to the criterion until after Meditation III. In Meditation III itself his only appeal is to the ‘natural light’, and he explicitly states that the cogito is also established by the natural light (A&T.VII.38). Significantly, the natural light fades out of the picture after God’s existence as a non-deceiver has been established.

It is tempting to associate the natural light with the process of mystical illumination, and the criterion of clear and distinct ideas with the process of re-establishing a dualistic account of reality. However, although this must be broadly correct, there are two respects in which the match is imperfect. First, in order to avoid the ‘Cartesian circle’, the natural light has to be used for the initial stage of the return from mystical illumination to the re-establishment of dualism. Without it, Descartes would remain trapped as a mode of infinite thought contemplating clear and distinct ideas with no concrete reference. Second, there is a sense in which the two arguments for the existence of God come in the wrong order. Given Descartes’ decision to base the argument in Meditation III on the natural light, and the ontological argument in Meditation V on the criterion of clear and distinct ideas, they must of course come in the order they do. But the second argument is more appropriate as the expression of a vision of God as a being in whom essence and existence coincide (A&T.VII.66), whereas the first argument establishes the distinction between the real existence of God, and his essence as grasped by Descartes’ mind. It would have been neater if Descartes had started with a full analysis of God’s nature, and only then argued for his separate real existence. [n.17]

Let us now turn to matter. If my interpretation is correct, Descartes’ starting point is a single vision of all that is clearly and distinctly perceived by the light of nature. As he says in Meditation III:

His problem is how, and how far, to separate the essence of matter from God’s essence, from Descartes’ own essence as thinking substance, and from the existence of matter. Descartes never even attempts the first. Indeed, the implication of passages like the above is that materiality is as much part of God’s essence as is thought — a view made explicit by Spinoza.

The separation of the essence of matter from the essence of thought is the dominant theme of the Meditations; and the central argument is that thinking substance has a direct awareness of both its essence and its existence, whereas thinking the concept of matter does not involve a direct awareness of its existence.

But what is the relation between the essence and the existence of matter? The essence of matter is extension. Extension is a ‘principal attribute’, which is not really distinct from material substance, and which can manifest itself only through its various ‘modes’, or particular ways of being extended. Nothing can be truly predicated of it except modes of extension (including motion, which is nothing other than a change in the configuration of matter from one instant to the next). However, none of this serves to anchor matter in reality. Simply to call it a substance doesn’t help if it is still essentially a universal rather than a particular. A Platonist such as Descartes could equally well describe number as a substance, on the grounds that it has an abstract existence independent of, and indeed prior to, the existence of numbered things. The parallel is all too close, since extension as an abstract universal is nothing other than the subject-matter of geometry, as number is of arithmetic; and one of Descartes’ greatest inventions was analytic geometry, which reduced geometry to a form of algebra requiring no spatial or extended representation. So, although extension is particularised through its modes, there is no reason why these modes should be individual existents. A particular shape (e.g. an equilateral triangle) is just as much an abstraction as a particular number.

I think there is a genuine conflict in Descartes’ thought here. On the one hand there is the Platonic-idealist view that only universals are real, and that they are known to universal human reason through clear and distinct (i.e. non-sensory) innate ideas. Matter as extension is just one of these innate ideas, and its science is a sort of temporalised geometry, known only by reasoning. On this view, the world of sense experience is so remotely connected (if at all) to the science of extension as to be of no interest to the philosopher. Hence Descartes’ extreme claim in Meditation II that he knows the nature not merely of wax in general, but of a particular piece of wax only through mental inspection (A&T.VII.31). Again, in the Principles he is remarkably casual about whether or not his detailed account of matter is true of the world of experience. For example, in III.47, he writes:

Similarly, in IV.204, he argues that:

On the other hand, Descartes did clearly believe in the concrete existence of material substance, however difficult it might be to square it with his Platonism. God would be a deceiver if the clear and distinct idea of matter did not correspond to a reality with precisely that nature; and his acceptance of the importance of experience and experiment in science is well documented. But the material world whose existence is reinstated in Meditation VI is utterly different from the world of experience. It has no properties in common, since even the modes of extension understood by the mind are different from the shapes and sizes perceived through the senses; and there is no real distinction between one physical object and another. So how can he say, as he does in Meditation II, that the wax he perceives with his mind is the same as the wax he sees, and touches, and imagines?

In the passage about the wax, there is a hint of the theory, later to be developed by Leibniz, that the difference between sensory and intellectual perception is one of degree — that what is obscure and confused in sensation becomes clear and distinct through intellection:

But this option is not open in a dualistic context. The message of Meditation VI is that sense perception is not an avenue to knowledge, and that it is a wilful error on the part of human beings to take it as such. Sense perception is primarily a physical phenomenon. It registers information about particulars, and it is designed to serve the needs of the body. Real knowledge is about universals, and it is the province of Reason.

This raises the question of the relation between sense perception and intellection. One approach is to see it as a particular instance of the more general mind/body problem — the problem of how there can be any connection at all between mind and matter, if they are substances totally disparate in nature. How can the mind be said to perceive?

For Descartes, there are two substances, thought and extension, and everything in the universe must be a mode of one or the other. It is relatively straightforward to apportion what were later called the ‘primary’ qualities of matter to extension, and modulations in a stream of abstract thought to mind. The problem is where to locate perceptions and imaginings of particular physical objects and events. At one level the answer is perfectly simple: they are configurations of the ‘animal spirits’ in the brain. As such they are purely physical, and no different from similar configurations in the brains of animals. In both cases they can do their work of mediating stimuli and responses through their action on the pineal gland without the need for any consciousness. Animals are just like sleepwalkers — the contents of their brains are not illuminated by consciousness. But what to say of the conscious perceptions of human beings? Now sometimes Descartes treats them, even if only as an afterthought, as modifications of the mind. For example, in Meditation II:

But this simply will not do. An extended imagination or perception cannot be a mode of unextended thought. Descartes was aware of the difficulty. As he wrote to Mersenne on 21.4.1641 (A&T.III.361–2):

This makes it clear that the images are not in the mind. It also implies that perception is an action of the mind rather than a passion.

Descartes was unusual in not making activity an essential characteristic of the soul; yet he was heavily influenced by the Platonic, Aristotelian, and Stoic tradition of seeing the soul as the active principle of the body. Although he grudgingly allowed the soul to be influenced by the body, he was much happier with the idea of the soul exerting its will over the body, and he regarded the ‘passions of the soul’ as something to be avoided as far as possible. Even if the soul is in fact more intimately related to the body than a captain is to his ship, the philosopher should strive to maintain a separation. When the body is damaged, for example, the soul should distance itself from the sensation of pain in the brain, and regard it as no more than an item of information about the state of the body, rather as the captain of a ship receives the news that the ship has sprung a leak.

One might compare Descartes’ general position on the soul’s awareness of what is happening in the body with that of St. Augustine in De musica, Bk. II, ch. v (‘Whether the soul is passive with respect to the body, and how it operates’) [n.23]:

Nevertheless, the relationship between active Reason and physical images in the brain remains mysterious. It is as if the mind shines the torch of consciousness on pictures in the dark caverns of the brain. But this is only an analogy; and no mechanism is provided — not even a metaphysical mechanism. Conveniently, Clerselier’s illustrations to the Traité de l'homme show the animal spirits crossing, so that the images of objects are the right way up on the surface of the pineal gland; but there can be no illustration of the soul ‘directing itself towards’ the images. [n.24] At least Descartes avoids going down the route of explaining how the soul perceives images in the brain by postulating mental ideas corresponding to the physical images.

The analogy implicit in Descartes’ account of perception is strikingly similar to Plato’s analogy of the cave. Plato’s message was that we should stop watching the shadow-puppets in the cave, and turn our eyes towards the sun, as the source of intellectual illumination. Descartes was too attracted by the shadow-puppets to be a consistent Platonist. He had an innate curiosity about the phenomena of nature, which he indulged freely. But he was too attracted by Platonism to develop a coherent account of how these phenomena are based in reality, or of how our rational understanding of a world of matter is related to our sensory perception of a world which presents a wholly different face.

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