I really see no harm which can come of giving our children a little knowledge of physiology. ... The instruction must be real, based upon observation, eked out by good explanatory diagrams and models, and conveyed by a teacher whose own knowledge has been acquired by a study of the facts; and not the mere catechismal parrot-work which too often usurps the place of elementary teaching.

The Bible account of the creation of Eve is a preposterous fable.

Friendship involves many things but, above all the power of going outside oneself and appreciating what is noble and loving in another.

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

The rules of the game are what we call the laws of nature.

The whole analogy of natural operations furnishes so complete and crushing an argument against the intervention of any but what are termed secondary causes, in the production of all the phenomena of the universe; that, in view of the intimate relations between Man and the rest of the living world; and between the forces exerted by the latter and all other forces, I can see no excuse for doubting that all are co-ordinated terms of Nature's great progression, from the formless to the formed from the inorganic to the organic from blind force to conscious intellect and will.

Only one absolute certainty is possible to man, namely that at any given moment the feeling which he has exists.