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.

But I cannot forget that, at other times I have been deceived in sleep by similar illusions; and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming.

We call infinite that thing whose limits we have not perceived, and so by that word we do not signify what we understand about a thing, but rather what we do not understand.

For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it.

Human wisdom remains always one and the same although applied to the most diverse objects and it is no more changed by their diversity than the sunshine is changed by the variety of objects which it illuminates.

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

And as it is the most generous souls who have most gratitude, it is those who have most pride, and who are most base and infirm, who most allow themselves to be carried away by anger and hatred.