The course of human history is determined, not by what happens in the skies, but what takes place in our hearts.

It is just because civilization is ever evolving, changing, and becoming more complicated, that experts find it so difficult to define it in explicit terms.

Religious leaders and men of science have the same ideals; they want to understand and explain the universe of which they are part; they both earnestly desire to solve, if a solution be ever possible, that great riddle: Why are we here?

Human nature, as manifested in tribalism and nationalism, provides the momentum of the machinery of human evolution.

Man is by nature competitive, combative, ambitious, jealous, envious, and vengeful.

A drunkard is one thing, and a temperate man is quite another.

Tolerance is held to be a condition of mind which is encouraged by, and is necessary for, civilization.