when we are asleep, while there is at that time not one of them true, I
supposed that all the objects (presentations) that had ever entered into
my mind when awake, had in them no more truth than the illusions of my
dreams. But immediately upon this I observed that, whilst I thus wished to
think that all was false, it was absolutely necessary that I, who thus
thought, should be somewhat; and as I observed that this truth, I think,
therefore I am (COGITO ERGO SUM), was so certain and of such evidence that
no ground of doubt, however extravagant, could be alleged by the sceptics
capable of shaking it, I concluded that I might, without scruple, accept
it as the first principle of the philosophy of which I was in search

In the next place, I attentively examined what I was and as I observed
that I could suppose that I had no body, and that there was no world nor
any place in which I might be; but that I could not therefore suppose that
I was not; and that, on the contrary, from the very circumstance that I
thought to doubt of the truth of other things, it most clearly and
certainly followed that I was; while, on the other hand, if I had only
ceased to think, although all the other objects which I had ever imagined
had been in reality existent, I would have had no reason to believe that I
existed; I thence concluded that I was a substance whose whole essence or
nature consists only in thinking, and which, that it may exist, has need
of no place, nor is dependent on any material thing; so that " I," that is
to say, the mind by which I am what I am, is wholly distinct from the
body, and is even more easily known than the latter, and is such, that
although the latter were not, it would still continue to be all that it is.

After this I inquired in general into what is essential I to the truth and
certainty of a proposition; for since I had discovered one which I knew to
be true, I thought that I must likewise be able to discover the ground of
this certitude. And as I observed that in the words I think, therefore I