...it is certain that I am really distinct from my body, and can exist without it.

For each of us there is a set limit to our intellectual powers which we cannot pass.

If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.

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.

Archimedes, that he might transport the entire globe ... demanded only a point that was firm and immovable; so also, I shall be entitled to entertain the highest expectations, if I am fortunate enough to discover only one thing that is certain and indubitable.

All is to be doubted.

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has.