A man's worst difficulties begin when he is able to do as he likes.

Time, whose tooth gnaws away everything else, is powerless against truth.

What men of science want is only a fair day's wages for more than a fair day's work.

My business is to teach my aspirations to confirm themselves to fact, not to try and make facts harmonize with my aspirations.

If then, said I, the question is put to me would I rather have a miserable ape for a grandfather or a man highly endowed by nature and possessing great means and influence and yet who employs those faculties for the mere purpose of introducing ridicule into a grave scientific discussion-I unhesitatingly affirm my preference for the ape.

The saying that a little knowledge is a dangerous thing is, to my mind, a very dangerous adage. If knowledge is real and genuine, I do not believe that it is other than a very valuable posession, however infinitesimal its quantity may be. Indeed, if a little knowledge is dangerous, where is a man who has so much as to be out of danger?

Man's Place in Nature.