How so many absurd rules of conduct, as well as so many absurd religious beliefs, have originated, we do not know; nor how it is that they have become, in all quarters of the world, so deeply impressed on the minds of men; but it is worthy of remark that a belief constantly inculcated during the early years of life, while the brain is impressionable, appears to acquire almost the nature of an instinct; and the very essence of an instinct is that it is followed independently of reason.

It is a fatal fault to reason whilst observing, though so necessary beforehand and so useful afterwards.

The limit of man s knowledge in any subject possesses a high interest which is perhaps increased by its close neighbourhood to the realms of imagination.

The age-old and noble thought of 'I will lay down my life to save another,' is nothing more than cowardice.

The season of love is that of battle. The roots of these fights run deep.

In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment.

It is certain that there may be extraordinary mental activity with an extremely small absolute mass of nervous matter: thus the wonderfully diversified instincts, mental powers, and affections of ants are notorious, yet their cerebral ganglia are not so large as the quarter of a small pin's head. Under this point of view, the brain of an ant is one of the most marvelous atoms of matter in the world, perhaps more so than the brain of a man.