The principle which underlies the reasoning of Descartes is that to be conscious of a limit, is to transcend it. We could not feel the limits either upon our thought or upon our existence, we could not doubt or desire, if we did not already apprehend something beyond these limits. Nay, we could not be conscious of our existence as individual selves if we were not conscious of that which is not ourselves, and of a unity in which both self and not-self are included. Our individual life is therefore to us as self-conscious beings a part of a wider universal life. Doubt and aspiration are but the manifestation of this essential division and contradiction of a nature which, as conscious of itself, is at the same time conscious of the whole in which it is a part. And as the existence of a self and its consciousness are one, so we may say that a thinking being is not only an individual, but always in some sense identified with that universal unity of being to which it is essentially related.
If Descartes had followed out this line of thought, he would have been led at once to the pantheism of Spinoza, if not beyond it. As it is, he is on the verge of contradiction with himself when he speaks of the consciousness of God as _in some sense_ prior to the consciousness of self. How can anything be prior to the first principle of knowledge? It is no answer to say that the consciousness of God is the _principium essendi_, while the consciousness of self is the _principium cognoscendi_. For, if the idea of God is prior to the idea of self, knowledge must begin where existence begins, with God. The words "in some sense," with which Descartes qualifies his assertion of the priority of the idea of God, only betray his hesitation and his partial consciousness of the contradiction in which he is involved. Some of Descartes's critics presented this difficulty to him in another form, and accused him of reasoning in a circle when he said that it is because God cannot lie that we are certain that our clear and distinct ideas do not deceive us. The very existence of the conscious self, the _cogito, ergo sum_, which is the first of all truths and therefore prior in certitude to the existence of God, is believed only because of the clearness and distinctness with which we apprehend it. How then, they argued, could God's truthfulness be our security for a principle which we must use in order to prove the being of God? The answer of Descartes is somewhat lame. We cannot doubt any self-evident principle, or even any truth based on a self-evident principle, when we are directly contemplating it in all the necessity of its evidence; it is only when we forget or turn away from this evidence, and begin to think of the possibility of a deceitful God, that a doubt arises which cannot be removed except by the conviction that God is true.[5] It can scarcely be said that this is a _dignus vindice nodus_, or that God can fitly appear as a kind of second-best resource to the forgetful spirit that has lost its direct hold on truth and its faith in itself. God, truth, and the human spirit are thus conceived as having merely external and accidental relations with each other. What Descartes, however, is really expressing in this exoteric way is simply that beneath and beyond all particular truths lies the great general truth of the unity of thought and existence. In contemplating particular truth, we may not consciously relate it to this unity, but when we have to defend ourselves against scepticism we are forced to realize this relation. The ultimate answer to any attack upon a special aspect or element of truth must be to show that the fate of truth itself, the very possibility of knowledge, is involved in the rejection of it, and that we cannot doubt it without doubting reason itself. But to doubt reason is, in the language of Descartes, to doubt the truthfulness of God, for, in his view, the idea of God is involved in the very constitution of reason. Taken in this way then, the import of Descartes's answer is, that the consciousness of self, like every other particular truth, is not at first seen to rest on the consciousness of God, but that when we realize what it means we see that it does so rest. But if this be so, then in making the consciousness of self his first principle of knowledge, Descartes has stopped short of the truth. It can only be the first principle if it is understood, not as the consciousness of the individual self, but in a sense in which the consciousness of self is identical with the consciousness of God.