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

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

Let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something.

Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.

Reason is nothing without imagination.

Even those who have the weakest souls could acquire absolute mastery over all their passions if we employed sufficient ingenuity in training and guiding them.

Now therefore, that my mind is free from all cares, and that I have obtained for myself assured leisure in peaceful solitude, I shall apply myself seriously and freely to the general destruction of all my former opinions.