The scientific imagination always restrains itself within the limits of probability.

Economy does not lie in sparing money, but in spending it wisely.

Not only does every animal live at the expense of some other animal or plant, but the very plants are at war.... The individuals of a species are like the crew of a foundered ship, and none but good swimmers have a chance of reaching the land.

If individuality has no play, society does not advance; if individuality breaks out of all bounds, society perishes.

And when you cannot prove that people are wrong, but only that they are absurd, the best course is to let them alone.

As a natural process, of the same character as the development of a tree from its seed, or of a fowl from its egg, evolution excludes creation and all other kinds of supernatural intervention.

What men of science want is only a fair day's wages for more than a fair day's work.