He who hid well, lived well.

Doubt is the origin of wisdom

I am thinking, therefore I exist. (...) I was a substance whose whole essence or nature is solely to think, and which does not require any place, or depend on any material thing, in order to exist. Accordingly this 'I' - that is, the soul by which I am what I am - is entirely distinct from the body, and indeed is easier to know than the body, and would not fail to be whatever it is, even if the body did not exist.

The only secure knowledge is that I exist.

I am indeed amazed when I consider how weak my mind is and how prone to error.

If ... it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power, namely, suspend judgement.

At last I will devote myself sincerely and without reservation to the general demolition of my opinions.