The only thing that I know, is that I know nothing

Each problem that I solved became a rule, which served afterwards to solve other problems.

In order to improve the mind, we ought less to learn, than to contemplate.

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

There is a little gland in the brain in which the soul exercises its functions in a more particular way than in the other parts.

So blind is the curiosity by which mortals are possessed, that they often conduct their minds along unexplored routes, having no reason to hope for success, but merely being willing to risk the experiment of finding whether the truth they seek lies there.

... moral certainty is certainty which is sufficient to regulate our behaviour, or which measures up to the certainty we have on matters relating to the conduct of life which we never normally doubt, though we know that it is possible, absolutely speaking, that they may be false.