It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.
An American monkey, after getting drunk on brandy, would never touch it again, and thus is much wiser than most men.
A man's friendships are one of the best measures of his worth.
The mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an agnostic.
The highest possible stage in moral culture is when we recognize that we ought to control our thoughts.
To kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact.
A scientific man ought to have no wishes, no affections, - a mere heart of stone.
I am turned into a sort of machine for observing facts and grinding out conclusions.
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.
