The feeling of health can only be gained by sickness.

I ceased in the year 1764 to believe that one can convince one’s opponents with arguments printed in books. It is not to do that, therefore, that I have taken up my pen, but merely so as to annoy them, and to bestow strength and courage on those on our own side, and to make it known to the others that they have not convinced us.

One of the greatest creations of the human mind is the art of reviewing books without having read them.

If nature be regarded as the teacher and we poor human beings as her pupils, the human race presents a very curious picture. We all sit together at a lecture and possess the necessary principles for understanding it, yet we always pay more attention to the chatter of our fellow students than to the lecturer's discourse. Or, if our neighbor copies something down, we sneak it from him, stealing what he himself may have heard imperfectly, and add it to our own errors of spelling and opinion.

Libraries can in general be too narrow or too wide for the soul.

Most men of education are more superstitious than they admit - nay, than they think.

We often have need of a profound philosophy to restore to our feelings their original state of innocence, to find our way out of the rubble of things alien to us, to begin to feel for ourselves and to speak ourselves, and I might almost say to exist ourselves.