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 PRINCIPLES OF THE SYSTEM. 89 peat them after others, before we have come into the full possession of our intellectual powers ; so that it is no wonder that we are filled with a multitude of prejudices, from which we can thoroughly escape only by considering eve iy thing doubtful which shows the least sign of uncer- tainty. Let us renounce, therefore, all our old views, in order later to accept better ones in their stead ; or, perchance, to take the former up again after they shall have stood the test of rational criticism. The recognized precaution, never to put complete confidence in that which has once deceived us, holds of our relation to the senses as elsewhere. It is certain that they sometimes deceive us — perhaps they do so always. Again, we dream every day of things which nowhere exist, and there is no certain criterion by which to distinguish our dreams from our waking moments,- — what guarantee have we, then, that we are not always dreaming? Therefore, our doubt must first of all be directed to the ex- istence of sense-objects. Nay, even mathematics must be suspected in spite of the apparent certainty of its axioms and demonstrations, since controversy and error are found in it also. I doubt or deny, then, that the world is what it appears to be, that there is a God, that external objects exist, that I have a body, that twice two are four. One thing, how- ever, it is impossible for me to bring into question, namely, that I myself, who exercise this doubting function, exist. There is one single point at which doubt is forced to halt — at the doubter, at the self-existence of the thinker. I can doubt everything except that I doubt, and that, in doubting, I am. Even if a superior being sought to de- ceive me in all my thinking, he could not succeed unless I existed, he could not cause me not to exist so long as I thought. To be deceived means to think falsely; but that j have written on Cartesianism. [The Method, Meditations, and Selections from the Principles have been translated into English by John Veitch, 5th ed., 1879, and others since ; and H. A. P. Torrey has published The Philosophy of Descartes in Extracts from his fF»-?V«M^j, 1892 (Sneath's Modern Philosopiicr,^;. The English reader may be referred, also, to Mahaffy's Descartes, iS3o, in Black- wood's Philosophical Classics; to the article "Cartesianism," Encyclopcrdia Britannica, 9th ed., vol. v., by Edward Caird ; and, for a complete discussion, to the English translation of Fischer's Descartes and his School by J. P. Gordy l3S7— Tr.]