Supposing himself for a moment in universal doubt, without accepting for certain anything that is known, he concentrated himself on himself, and in the depth of his soul sought a point whereon to base the edifice of human cognitions. Although we abstract all around us, we clearly cannot abstract ourselves, our mind, which is present to its own eyes, only the more lucidly, the greater the abstraction in which we place ourselves with respect to eternal objects. Now in this concentration, this collection of himself within himself, this withdrawal from every thing for fear of error, and asking himself if there be any thing certain, if there be any foundation and starting-point in the career of knowledge; first of all is presented to him the consciousness of thought, the very presence of the acts of his mind. If we mistake not, this was Descartes' thought: I wish to doubt of every thing; I refrain from affirming as from denying any thing; I isolate myself from whatever surrounds me, because I know not if it be any thing more than an illusion. But in this very isolation, I meet with the intimate sense of my internal acts, with the presence of my mind; I think, therefore I am; this I feel in a manner that leaves no room for doubt or uncertainty; therefore, I am; that is to say, this sense of my thought makes me know my existence. 169. This explains why Descartes did not present his principle as a mere enthymema, as an ordinary argument, but as determining a fact presented to him and first in the order of facts: even if he inferred existence from thought, it was not by deduction, properly so called, but as one fact contained in another, or rather identified with it.