It ought not to be unpleasant to say that which one honestly believes or disbelieves. That it so constantly is painful to do so, is quite enough obstacle to the progress of mankind in that most valuable of all qualities, honesty of word or of deed.

Whatever evil voices may rage, Science, secure among the powers that are eternal, will do her work and be blessed.

There is no absurdity in theology so great that you cannot parallel it by a greater absurdity in Nature.

I care not what subject is taught, if only it be taught well.

The great tragedy of science - the slaying of a beautiful hypothesis by an ugly fact.

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

The doctrine of transmigration… was a means of constructing a plausible vindication of the ways of the cosmos to man; … none but very hasty thinkers will reject it on the grounds of inherent absurdity.