The world is neither wise nor just, but it makes up for all its folly and injustice by being damnably sentimental.

I would rather be the offspring of two apes than be a man and afraid to face the truth.

Social progress means a checking of the cosmic process at every step and the substitution for it of another, which may be called the ethical process; the end of which is not the survival of those who may happen to be the fittest, in respect of the whole of the conditions which obtain, but of those who are ethically the best.

The ultimate court of appeal is observation and experiment... not authority.

Common sense is science exactly in so far as it fulfills the ideal of common sense; that is, sees facts as they are, or at any rate, without the distortion of prejudice, and reasons from them in accordance with the dictates of sound judgment. And science is simply common sense at its best, that is, rigidly accurate in observation, and merciless to fallacy in logic.

Regarded anatomically, the resemblances between the foot of Man and the foot of the Gorilla are far more striking and important than the differences... be the differences between the hand and foot of Man and those of the Gorilla what they may the differences between those of the Gorilla and those of the lower Apes are much greater.

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.