If a man cannot do brain work without stimulants of any kind, he had better turn to hand work it is an indication on Nature's part that she did not mean him to be a head worker.

Our reverence for the nobility of manhood will not be lessened by the knowledge that man is in substance and in structure, one with the brutes; for he alone possesses the marvellous endowment of intelligible and rational speech whereby he has slowly accumulated and organized the experience which is almost wholly lost with the cessation of individual life in other animals; so that he now stands raised above it as on a mountain-top, far above the level of his humble fellows, and transfigured from his grosser nature by reflecting, here and there, a ray from the infinite source of truth.

The facts of variability, of the struggle for existence, of adaptation to conditions, were notorious enough; but none of us had suspected that the road to the heart of the species problem lay through them, until Darwin and Wallace dispelled the darkness.

Time, whose tooth gnaws away everything else, is powerless against truth.

In science, as in art, and, as I believe, in every other sphere of human activity, there may be wisdom in a multitude of counsellors, but it is only in one or two of them.

[Scientists] have learned to respect nothing but evidence, and to believe that their highest duty lies in submitting to it however it may jar against their inclinations.

Mathematics may be compared to a mill of exquisite workmanship, which grinds your stuff to any degree of fineness.