R ESULTADOS

In establishing his own existence, so long as he is thinking (see Chapter 2, p. 41), Descartes formed a conception of himself as a res cogitans, a thinking thing. Thought alone, of all the properties he has hitherto attributed to himself, cannot conceivably be separated from him in any sceptical scenario, no matter how 'hyperbolical', that he can invent. I may perhaps have other properties, says Descartes in the Second Meditation; but if I confine myself to what cannot conceivably be doubted I am left with the notion of a 'thing that thinks'. 'Thinking', Descartes explains, comprises the whole range of conscious activity: 'But what am I? A thing that thinks. What is that? A thing that doubts, understands, is willing, is unwilling, and also imagines and has sensory perceptions' ( AT VII. 28; CSM II. 19).

In an attempt to break out of the enclosed realm of his subjective consciousness, Descartes proceeds, in the Third Meditation, to make a survey of the ideas he finds within his

consciousness; the 'first and most important' idea he becomes aware of is the idea of God. By this term 'God', he tells us, he means 'a substance that is infinite, eternal, immutable,

independent, supremely intelligent, supremely powerful, and which created both myself, and everything else (if anything else there be) that exists' ( AT VII. 45; CSM II. 31).

Descartes's subsequent argument for God's existence, which has been exhaustively analysed by commentators, depends on a principle which he says is 'manifest by the natural light':

'there must be at least as much in the cause as in the effect', or (as he later formulates it), 'there is nothing in the effect that was not previously present either in a similar or a higher form in the cause' ( AT VII. 135; CSM II. 97). Thus all the reality which is present in a stone must, says Descartes, be present in some way in the cause

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of the stone, whatever it may be ( AT VII. 41; CSM II. 28). This principle (which we may dub the 'causal adequacy principle') is taken by Descartes to apply not just to ordinary effects (such as stones), but also to ideas in the mind, and in particular to what we may call their 'representational content' (or what Descartes calls their 'objective reality' ⁸ ). If I examine what is contained or represented in my idea of God I find that what is represented is a substance that is infinite, eternal, etc; and, according to the causal adequacy principle, these various perfections that are contained in the idea must be present in whatever caused the idea. Now I can hardly be the cause of this idea since I am certainly not infinite (as I know from many imperfections, such as my ignorance on many topics). 'I could not', says Descartes, 'have the idea of an infinite substance, when I am finite, unless this idea proceeded from some

substance which really was infinite' ( AT VII. 45; CSM II. 31). Hence this infinite substance necessarily exists.

There is of course much in this reasoning (even in the highly compressed summary just given) that might be debated. Nicolas Malebranche, writing some thirty years after Descartes's death, displays an interestingly ambivalent attitude towards proofs based on the idea of God. On the one hand he observes that 'of the proofs of God's existence, the loftiest, the most beautiful, the primary and most solid . . . is that which invokes the idea we have of the infinite'. ⁹ But Malebranche goes on to insist that when we are aware of God, we are directly united with God himself--we see God directly and immediately, and not through the medium of any representative idea of the kind Descartes posited. Descartes maintained that although I myself am an imperfect created being, I none the less find within my mind a representation of the infinite; Malebranche replied that it is inconceivable for a created thing to represent the infinite. ¹⁰

This issue became a major bone of contention between Malebranche and Antoine Arnauld during the 1680s and 1690s. Arnauld had earlier criticized certain aspects of Descartes's proof (in his Fourth Set of Objections of 1641); but forty years later, in his "'True and False Ideas'" ( Des vraies et fausses idées, 1683), he launched a major attack on Malebranche in the course of which

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he supported the Cartesian notion of an idea as essentially representative of its object. ¹¹ 'It is not true', he later wrote to Malebranche, 'that a modality of our soul, which is finite, cannot represent an infinite thing; on the contrary, however finite our perceptions may be, there are some which have to be understood as infinite in the sense that they represent the infinite' (letter of 22 May 1694).

The prolonged and complex debate between Arnauld and Malebranche over the status of the idea of God cannot be evaluated here. But two general aspects of it are worth underlining.

First, the debate illustrates something it is easy to forget from a twentieth-century perspective:

that Descartes's arguments for the existence of God generated as much, if not more, interest in the seventeenth century than his mathematics or physics or psychology. It is important to remember, moreover, that for Descartes the struggle to establish God's existence was not, so to speak, a self-contained problem, one which could be relegated, as it might be today, to a special compartment marked 'philosophy of religion'. On the contrary, without an effective proof of the existence of a creator who is all-perfect and the source of truth, the whole

Cartesian strategy for escaping from the subjective world of doubt, and establishing a reliable system of objective knowledge, crumbles away.

The second important aspect of the Malebranche-Arnauld debate is the doubt it casts on the supposedly straightforward nature of Cartesian metaphysics. Descartes himself claimed that his arguments were so simple, so free of obscurities and preconceptions, that they could be followed by any attentive person of simple good sense ( AT X. 502; CSM II. 403). But the exchange between Malebranche and Arnauld forcefully illustrates the extent to which even such a basic item of Descartes's vocabulary as the term 'idea' is fraught with problems. Even back in the 1640s Descartes had had trouble explaining exactly what he meant by this term.

Thomas Hobbes, in his Third Set of Objections, had taken the term to refer to some kind of simple image--a suggestion that Descartes adamantly rejected ( AT VII. 179; CSM II. 126).

But if not an image, what exactly is an idea? Is it simply a mode of thought, a 'modality of perception' as

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Arnauld interpreted it, or was it regarded by Descartes as some kind of intermediate mental entity (as Malebranche supposed)? What exactly does it mean to say that an idea 'represents' an object? And is it necessary to construe the representational relation in terms of some kind of resemblance? ¹² The points of controversy which emerge between Malebranche and Arnauld give a vivid sense of just how difficult is the Cartesian project of describing with unassailable clarity, and in a way which is free from all taint of preconceived opinion, the mental acts and processes of the meditator as he searches for knowledge.

If we turn now to more specific problems concerning Descartes's proof of God's existence from the idea of God, it is the causal adequacy principle which seems to present the greatest difficulty. Part of Descartes's reasoning for holding to the maxim 'nothing in the effect which was not previously present in the cause' seems to have been a rather crude 'heirloom' view of causation--that the only way an effect can come to have some property is by having it passed on, heirloom fashion, from its cause. This is close to the view which Bishop George Berkeley referred to some seventy years later as the 'old known axiom', 'Nothing can give to another that which it hath not itself.' ¹³ Such a thesis would appear to deny the possibility of 'emergent' properties (for example, the properties which emerge when two elements are compounded, even though they were not present in either of the constituents). Descartes does not, however,

insist that the features present in an effect should always be present in precisely the self-same form in its cause; ¹⁴ and elsewhere he accepts a rather more general formulation of the relation that must obtain between cause and effect: 'The effect is like the cause' ( AT V. 156; CB17). In its general formulation, this slogan seems to encapsulate Descartes's commitment to the notion of a rationally intelligible link between cause and effect. If an effect has some feature F, then that feature cannot (as he says elsewhere) have come from nothing; it must have been present, in some form, in the cause ( AT VII. 135; CSM II. 97). It follows from this that causal relations cannot be reducible to mere regularity or a repeated conjunction of events (as Hume was later to propose); rather, there must be some necessary connection--some link in

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terms of shared or common features--between cause and effect. ¹⁵ We shall return to this thesis later in this chapter, and also in the next, when we come to discuss the view taken by Descartes and the other rationalists of the nature of the apparent causal interactions between mind and body. ¹⁶

At this stage of his 'way of discovery', however, Descartes is not yet ready to make any assertions about the physical universe. He is simply aware first of himself as a thinking substance, and now, secondly, of God, the supremely powerful substance who created him and placed the idea of himself within him 'to be as it were, the mark of the craftsman stamped on his work' ( AT VII. 51; CSM II. 35). But Descartes has noted along the way that in addition to himself and God, he also finds within him the idea of 'extended, corporeal substance' or matter--that which occupies space and can be characterized in terms of length, breadth, and depth ( AT VII. 43; CSM II. 30). ¹⁷ Now the existence of an idea is no guarantee that anything corresponding to the idea actually exists; and the hyperbolical doubts of the First Meditation have raised the possibility that the whole external world is a 'chimera'. The situation is radically altered, however, once Descartes has (or takes himself to have) established the existence of a perfect God who is the source of truth and who would not allow him to be systematically deceived. Given this foundation of certainty, Descartes can proceed to invoke a fact that he was aware of all along, namely his strong propensity to believe that his ideas of corporeal objects come directly from external objects. In the light of this, he does not see 'how God could be anything other than a deceiver if the ideas were transmitted from a source other than corporeal things' ( AT VII. 80; CSM. II. 55). It follows, Descartes concludes in the Sixth Meditation, that the external world does indeed exist; and although many of his sensory impressions of that world may be confused and misleading, at least he has some prospect of developing a reliable physical theory, provided he confines himself to his clear and distinct ideas of corporeal substance, that is, 'all those which viewed in general terms are comprised within the subject matter of pure mathematics' (ibid.).

From this very brief résumé, it should at least be clear that by the end of his metaphysical meditations, Descartes has

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established the existence of three substances: first, himself, res cogitans or thinking

substance; second, God, the infinite substance who created him; and third, matter or extended substance. ¹⁸ In the Meditations, which is designed to avoid technical language as far as possible, Descartes does not do very much to unpack the notion of substance; indeed, he prefers wherever possible to avoid the Latin term substantia, speaking instead of res cogitans

and res extensa (literally 'thinking thing' and 'extended thing'. Cf. AT VII. 78; CSM II. 54). ¹⁹ But in his 1644 Principles of Philosophy, which was designed as an academic textbook, Descartes goes into much more detail. Starting from the scholastic idea that the term

substance conveys the notion of something which 'depends on no other thing for its existence' (see above, p. 77), Descartes remarks that it is only God who qualifies as a substance in the strict sense of depending on 'no other thing whatsoever'. (The whole of Spinoza's

metaphysics, as we shall see, can in a sense be seen as a meditation on this one thought.) But a created thing can, Descartes asserts, be considered as a substance in a secondary sense, in so far as, unlike qualities or attributes which can only exist 'in' something else, it can be said to exist 'on its own', needing nothing else (except of course for the continuous divine action of God which preserves it, or keeps it in existence: Principles I, 51-2). ²⁰

With regard to created substance, we can, Descartes asserts, have two clear and distinct notions or ideas--one of thinking substance, the other of extended substance. Extension and thought are the 'principal attributes' of matter and mind respectively:

Each substance has one principal property which constitutes its nature or essence and to which all its other properties are referred. Thus extension in length, breadth and depth constitutes the nature of corporeal substance, and thought constitutes the nature of thinking substance. Everything else which can be attributed to body presupposes extension and is merely a mode of an extended thing; and similarly whatever we find in mind is simply one of the various modes of thinking ( Principles I, 53).

Here in a nutshell is Descartes's celebrated 'dualistic' theory of substance, according to which all the various features we

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attribute to things are reducible to 'modes' or modifications either of thinking stuff or of extended stuff. But on closer examination this apparently very tidy schema begins to lose some of its symmetry.