It is somewhat curious, and, as an illustration of the frivolous verbal disputes of philosophers, not a little instructive, that this celebrated "_Cogito, ergo sum_," should have been frequently attacked for its logical imperfection. It has been objected, from Gassendi downward, that to say, "I think, therefore I am," is a begging of the question; since existence has to be proved identical with thought. Certainly, if Descartes had intended to prove his own existence by reasoning, he would have been guilty of the _petitio principii_ Gassendi attributes to him, viz., that the major premise, "that which thinks exists," is assumed, not proved. But he did not intend this. What was his object? He has told us that it was to find a starting-point from which to reason--to find an irreversible certainty. And where did he find this? In his own consciousness. Doubt as I may, I cannot doubt of my own existence, because my very doubt reveals to me a something which doubts. You may call this an assumption, if you will: I will point out the fact as one above and beyond all logic; which logic can neither prove nor disprove; but which must always remain an irreversible certainty, and as such a fitting basis of philosophy. I exist. No doubt can darken such a truth; no sophism can confute this clear principle. This is a certainty, if there be none other. This is the basis of all science. It is in vain to ask for a proof of that which is self-evident and irresistible. I exist. The consciousness of my existence is to me the assurance of my existence. Had Descartes done no more than point out this fact he would have no claim to notice here; and we are surprised to find many writers looking upon this "_Cogito, ergo sum_" as constituting the great idea in his system. Surely it is only a statement of universal experience--an epigrammatic form given to the common-sense view of the matter. Any clown would have told him that the assurance of his existence was his consciousness of it; but the clown would not have stated it so well. He would have said, "I know I exist, because I feel that I exist."