A man's friendships are one of the best measures of his worth.

The very essence of instinct is that it's followed independently of reason.

Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.

On the ordinary view of each species having been independently created, we gain no scientific explanation.

False facts are highly injurious to the progress of science, for they often endure long; but false views, if supported by some evidence, do little harm, for every one takes a salutary pleasure in proving their falseness.

How paramount the future is to the present when one is surrounded by children.

At some future period, not very distant as measured by centuries, the civilized races of man will almost certainly exterminate, and replace the savage races throughout the world.

A man who dares to waste one hour of time has not discovered the value of life.

If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.

An American monkey, after getting drunk on brandy, would never touch it again, and thus is much wiser than most men.

To kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact.

I love fools' experiments. I am always making them.