To avoid the various foolish opinions to which mankind are prone, no superhuman genius is required. A few simple rules will keep you, not from all error, but from silly error.

Understanding human nature must be the basis of any real improvement in human life. Science has done wonders in mastering the laws of the physical world, but our own nature is much less understood, as yet, than the nature of stars and electrons. When science learns to understand human nature, it will be able to bring a happiness into our lives which machines and the physical sciences have failed to create.

We may define "faith" as the firm belief in something for which there is no evidence. Where there is evidence, no one speaks of "faith." We do not speak of faith that two and two are four or that the earth is round. We only speak of faith when we wish to substitute emotion for evidence. The substitution of emotion for evidence is apt to lead to strife, since different groups, substitute different emotions.

What Galileo and Newton were to the seventeenth century, Darwin was to the nineteenth.

It is not by delusion, however exalted, that mankind can prosper, but only by unswerving courage in the pursuit of truth.

There was, I think, never any reason to believe in any innate superiority of the male, except his superior muscle.

One is always a little afraid of love, but above all, one is afraid of pain or causing pain.