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On Cartesian Metaphysics

by Alfredo Lucero-Montano

The starting point of Descartes' philosophy is that we must 'doubt everything, as far as is possible,'[1] and this obviously represents an absolute beginning. This is Descartes' essential thesis of philosophy. Nevertheless, this first thesis does not entail a skeptical sense, whose aim is doubt itself. On the contrary, Descartes' doubt means that we must give up any prejudice and any proposition that we might directly accept as true, and take thought itself as a starting point to arrive to certainty and to establish, then, a pure beginning.[2] For Descartes, doubt is not a consequence, but a starting point.

Cartesian doubt means that no idea is either certain or indubitable, unless reason can separate itself from all preconceived opinions, namely, to think, because the pure thinking precisely consists in separating itself from uncertainty. What prevails in the Cartesian mind is the goal of arriving at something certain — objective — and not to just stand still at the subjective moment, but to arrive to something established, known and proven by reason. In Descartes' own words:

Since we began life as infants, and made various judgements concerning the things that can be perceived by the senses before we had the full use of our reason, there are many preconceived opinions that keep us from knowledge of truth. It seems that the only way of freeing ourselves from these opinions is to make the effort... to doubt everything which we find to contain even the smallest suspicion of uncertainty. This doubt... should be kept in check and employed solely in connection with the contemplation of the truth.[3]

This Cartesian reasoning, then, states that what is truth must be recognized within reason itself.

Descartes seeks something certain and true in itself, something that is not merely true like the object of faith — without knowledge — nor like sense certainty and skeptical certainty which lack truth. For Descartes, nothing is true but what has an inward certainty (in consciousness), or when reason knows in a clear and definite way, that is, when it excludes any possibility of doubt:

In rejecting... everything which we can in any way doubt, it is easy for us to suppose that there is no God and no heaven, and that there are no bodies, and even that we ourselves have no hands or feet, or indeed any body at all. But we cannot for all that suppose that we, who are having such thoughts, are nothing. For it is a contradiction to suppose that what thinks does not, at the very time when it is thinking, exist. Accordingly, this piece of knowledge -- I am thinking, therefore I exist — is the first and most certain of all to occur to anyone who philosophizes in an orderly way. This is the best way to discover the nature of mind and the distinction between the mind and the body. For if we, who are supposing that everything which is distinct from the false, examine what we are, we see very clearly that neither extension nor shape nor local motion, nor anything of this kind which is attributable to a body, belongs to our nature, but that thought alone belongs to it. So our knowledge of our thought is prior to, and more certain than, our knowledge of any corporeal thing.[4]

Therefore, Descartes does not understand the cogito as the individuality of consciousness of itself, but rather as the meaning of thought. This is precisely the the second Cartesian thesis, namely, the immediate certainty of thought. The certainty is nothing but knowledge as such, in its pure form, as reflected upon itself, which is thought.

The starting point of Descartes, then, is the cogito as the simply certain; what I know is that something presents or represents in me. His philosophy now moves toward the realm of subjectivity. The content of the proposition is abandoned, because it disappears facing an abstract subjectivity. Considering the content in itself is no longer important, for if I can abstract myself of all representations, I cannot abstract myself from the cogito. Thought is absolutely general, but not because the cogito can abstract itself, but because the cogito is this entity, both simple and identical with itself. Thought is the first determination; the one that follows is the determination of being. According to Descartes, the 'I think' involves directly my own being, and this is the absolute foundation of all philosophy.

It was necessary that I, who was thinking this, was something. And observing that this truth 'I am thinking, therefore I exist' was so firm and sure that all the most extravagant suppositions of the sceptics were incapable of shaking it, I decided that I could accept it without scruple as the first principle of the philosophy I was seeking.[5]

The determination of being is contained in my cogito, and this is the first relation. The thinking as being, and the being as thinking, is my certainty, my cogito; in the Cogito, ergo sum we find inseparably united thought and being.

This thesis — Cogito, ergo sum — seems constructed as a syllogism, as if from thought we can deduce being. Kant argues against this syllogistic mechanism, and he claims that thought does not contain being, for the latter is something different from thought. Of course, this is true, but it is no less true that both are inseparable, that is, we find an identity between both — its unity is not undermined by its diversity. Nevertheless, this absolute and pure certainty is not proven — the totality that is in itself. This is why we cannot turn this proposition into a deduction. In Descartes' own words:

When someone says 'I am thinking, therefore I am, or I exist', he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. This is clear from the fact that if he were deducing it by means of a syllogism, he would have to have had previous knowledge of the major premiss 'Everything which thinks is, or exists'; yet in fact he learns it from experiencing in his own case that it is impossible that he should think without existing.[6]

A syllogism is an argument consisting of three terms; here we should have a third term that would function as a mediator, as a link between thought and being, but this third term does not exist. The 'therefore' that links both thought and being is not the 'therefore' of a syllogism. Here the relation between thought and being is established in an immediate way. This certainty is a metaphysical priority.

Descartes, at this point, is not concerned to demonstrate the identity between being and thought, but just to refer to awareness or consciousness. He does not yet feel the necessity to develop the differences contained in the 'I think'. He only stresses the cogito, not on the rest of its content. For him, being is identical to pure thought, not the content of being, whatever it is.

By the term 'thought', I understand everything which we are aware of as happening within us, in so far as we have awareness of it. Hence, thinking is to be identified here not merely with understanding, willing and imagining, but also with sensory awareness. For if I say 'I am seeing, or I am walking, therefore I exist', and take this as applying to vision or walking as bodily activities, then the conclusion is not absolutely certain. This is because, as often happens during sleep, it is possible for me to think I am seeing or walking, though my eyes are closed and I am not moving about; such thoughts might even be possible if I had no body at all. But if I take 'seeing' or 'walking' to apply to the actual sense or awareness of seeing or walking, then the conclusion is quite certain, since it relates to the mind.[7]

With willing, seeing, etc., thought is implicit, because it would be absurd to believe that the mind keeps a special compartment for the faculty of thinking. However, when we say: 'I am seeing' or 'I am walking', on one hand, my consciousness, the cogito and, hence, thinking are implicit, and on the other, willing, seeing, walking, etc., and with it the content of consciousness is also implicit. And precisely this content prevents us from asserting 'I am walking, therefore I exist', for we can abstract ourselves from such mental occurrence since it is not thinking as such. We have to view the pure consciousness contained in this concrete cogito. When I exist in it as thinking being, only then I have before me the pure being, since this pure being can considered only in general and never in a particular state. Descartes writes:

In order to realize that the knowledge of our mind is not simply prior to and more certain than the knowledge of our body, but also more evident... as is manifest from the fact that whatever enables us to know anything else cannot but lead us to a much surer knowledge of our own mind. For example, if I judge that the earth exists from the fact that I touch it or see it, this very fact undoubtedly gives even greater support for the judgement that my mind exists. For it may perhaps be the case that I judge that I am touching the earth even though the earth does not exist at all; but it cannot be that, when I make this judgement, my mind which is making the judgement does not exist. And the same applies in other cases 'regarding all the things that come into our mind, namely that we who think of them exists, even if they are false or have no existence.'[8]

Here we see philosophy's proper realm, the basis on which thought starts from thought itself as something certain, and not from something exterior or given, but pure and simply from the activity that contains the 'I think'. Though I can doubt everything else, the existence of physical things, or my own body, still this certainty of the cogito has the property of the immediate. For the cogito is precisely the certainty itself, of which everything else is only the predicate; naturally, my body is certain for me, but is not certainty itself.

There are certain things that make us doubt the existence of our body. Therefore we shall not attain certainty of this except through the knowledge and certainty of something else that is prior to it in knowledge and certainty. Therefore the statement 'I am', insofar as 'I' am a thing consisting of body, is not a first principle and is not known through itself.[9]

For Descartes, the real is a substance, and the 'I' is the thinking substance; the latter exists for itself as something distinct and independent of all material and external things: 'From this I knew I was a substance whose whole essence or nature is simply to think, and which does not require any place, or depend on any material thing, in order to exist'.[10] Its thinking nature is self-evident: the mind would think and exist even if material things did not exist; that is why the mind is easier to know than the body.

Any truth we might have lies in this certainty, for anything we could hold as true needs this certainty in the inwardness of consciousness:

We must consider as most certainly true everything that is equally evident to us and that we perceive with the same clearness and distinctness as the already discovered first principle, and also everything that so agrees with this first principle and so depends on it that we cannot doubt it without also having to doubt this first principle (that is, this 'I').[11]

The knowledge of itself is perfect certainty, but it is not yet the truth. For if we considered this proposition as the truth, we only have a vacuous content, and it is precisely the content of truth — being — that the Cartesian project is all about.

I observed that there is nothing at all in the proposition 'I am thinking, therefore I exist' to assure me that I am speaking the truth, except that I see very clearly that in order to think it is necessary to exist.[12]

The issue now is the movement from certainty to truth. Descartes, at this point, offers us his metaphysics. The process involves the interest of other representations about the abstract unity of being and thought.

The mind... knowing itself, but still in doubt about all other things, looks around in all directions in order to extend its knowledge further. First of all, it finds within itself ideas of many things; and so long as it merely contemplates these ideas and does not affirm or deny the existence outside itself of anything resembling them, it cannot be mistaken. Next, it finds certain common notions from which it constructs various proofs; [and so long as it attends to the premises from which it deduced them]... it is completely convinced of their truth. But... recalling that it is still ignorant as to whether it may have been created with the kind of nature that makes it go wrong even in matters which appear most evident, the mind sees that it has just cause to doubt such conclusions.[13]

Descartes writes here that error, with respect to the representation, takes place in relation with exterior existence; for if the soul can exist without the corporeal, and the latter without the former, therefore, they are distinct realities, and thus the one can be conceived without the other.[14] Hence, the soul does not know with the same clarity and distinction the other as it knows the certainty of itself.

However, the truth of all knowledge entails the proof of the existence of God. The soul is an imperfect substance, but it has within itself the idea of an absolutely perfect substance; this perfection is not created by itself, for it is an imperfect one, hence, it is an innate idea.

The mere fact that I exist and have within me an idea of a most perfect being, that is, God, provides a very clear proof that God indeed exists. It only remains for me to examine how I received this idea from God. For I did not acquire it from the senses... .And it was not invented by me either... .The only remaining alternative is that it is innate in me, just as the idea of myself is innate in me.[15]

According to Descartes, while the existence of God is not proven and recognized, there is the possibility that we could be mistaken, due to our incapacity to know if our nature is really inclined to fall into error.

Given that we have within us an idea of the supreme perfection of God. Now it is certainly very evident by natural light that a thing which recognizes something more perfect than itself is not the source of its own being; for if so, it would have given itself all the perfection of which it has an idea. Hence, the source of its being can only be something which possesses within itself all these perfections — that is, God.[16]

Descartes here contrasts the consciousness of itself and the consciousness of the other (objectivity), but the real matter is the unity of both things, that is, how to know if what we discover in thought also has objectivity. However, this unity lies in God, that is, is God itself.

The mind next considers the various ideas which it has within itself, and finds that there is one idea — the idea of a supremely intelligent, supremely powerful and supremely perfect being — which stands out from all others.[17]
For when we reflect on the idea of God... we see that he is eternal, omniscient, omnipotent, the source of all goodness and truth... and finally that he possesses within him everything in which we can clearly recognize some perfection that is infinite.[18]

This general idea, which spans over everything, characterizes within it that there is no uncertainty about its being (existence), such as we observe in many other ideas. This idea guarantees the existence of its object.

In this one idea the mind recognizes existence — not merely the possible and contingent existence which belongs to the ideas of all the other things which it distinctly perceives, but utterly necessary and eternal existence. Now on the basis of its perfection that... necessary and eternal existence is contained in the idea of a supremely perfect being, the mind must clearly conclude that the supreme being does exist.[19]

The idea of perfection contains within it, as an effect, the property (determination) of existence, for we cannot assert that the concept (representation) of something not existent is perfect. Here we have the unity of thought and being or, in other words, the ontological argument for the existence of God. This is Descartes' attempt to deduce the existence of God from the idea of God: we understand God as a perfect being, nothing greater can be conceived, and since we have this idea, God exists. In sum, the argument for the existence of God, starting from its idea, entails its existence, and hence it is true.


1. Descartes, Principles of Philosophy (AT VIIIA 5), in The Philosophical Writings of Descartes, trans. J. Cottingham, R. Stoothoff and D. Murdoch, vol. 1 (Cambridge: Cambridge University Press, 1985).

2. Here the notion 'pure beginning' means, in a Kantian sense, that such beginning does not depend of any particular course of experience.

3. Ibidem (AT VIIIA 5-6).

4. Ibidem (AT VIIIA 7).

5. Descartes, Discourse on the Method (AT VI 32), in The Philosophical Writings of Descartes, trans. J. Cottingham, R. Stoothoff and D. Murdoch, vol. 1 (Cambridge: Cambridge University Press, 1985).

6. Descartes, Objections and Replies published together with the Meditations on First Philosophy (AT VII 140-141), in The Philosophical Writings of Descartes, trans. J. Cottingham, R. Stoothoff and D. Murdoch, vol. 2 (Cambridge: Cambridge University Press, 1984).

7. Descartes, Principles of Philosophy (AT VIIIA 7-8).

8. Ibidem (AT VIIIA 8-9).

9. Spinoza, The Principles of Cartesian Philosophy (PPCp3dem), trans. Samuel Shirley (Indianapolis: Hackett, 1998).

10. Descartes, On the Method (AT VI 33).

11. Spinoza (PPCp4schol).

12. Descartes, On the Method (AT VI 33).

13. Principles of Philosophy (AT VIIIA 10-11).

14. See Meditations, Med6 (AT VII 73).

15. Meditations, Med3 (AT VII 51).

16. Principles of Philosophy (AT VIIIA 12).

17. Ibidem (AT VIIIA 10).

18. Ibidem (AT VIIIA 13).

19. Ibidem (AT VIIIA 10).


Descartes, Principles of Philosophy. In The Philosophical Writings of Descartes. Trans. J. Cottingham, R. Stoothoff and D. Murdoch. Vol. 1. (Cambridge: Cambridge University Press, 1985).

___. Discourse on the Method. In The Philosophical Writings of Descartes. Trans. J. Cottingham, R. Stoothoff and D. Murdoch. Vol. 1. (Cambridge: Cambridge University Press, 1985).

___. Objections and Replies published together with the Meditations on First Philosophy. In The Philosophical Writings of Descartes. Trans. J. Cottingham, R. Stoothoff and D. Murdoch. Vol. 2. (Cambridge: Cambridge University Press, 1984).

Spinoza, Baruch. The Principles of Cartesian Philosophy. Trans. Samuel Shirley. (Indianapolis: Hackett, 1998).

© Alfredo Lucero-Montano 2007