If one hesitates in his path, let him not proceed. Let him respect his doubts, for doubts, too, may have some divinity in them.

He is not a true man of science who does not bring some sympathy to his studies, and expect to learn something by behavior as well as by application. It is childish to rest in the discovery of mere coincidences, or of partial and extraneous laws. The study of geometry is a petty and idle exercise of the mind, if it is applied to no larger system than the starry one. Mathematics should be mixed not only with physics but with ethics; that is mixed mathematics. The fact which interests us most is the life of the naturalist. The purest science is still biographical.

Be resolutely and faithfully what you are; be humbly what you aspire to be.

Friends are made for caring and sharing. Friends do not live in harmony merely, as some say, but in melody.

We should endeavor practically in our lives to correct all the defects which our imagination detects.

I should be glad if all the meadows on the earth were left in a wild state, if that were the consequence of men's beginning to redeem themselves.

We are the subjects of an experiment which is not a little interesting to me.