And you very soon find out, if you have not found it out before, that patience and tenacity of purpose are worth more than twice their weight of cleverness.

Men can intoxicate themselves with ideas as effectually as with alcohol or with bang and produce, be dint of serious thinking, mental conditions hardly distinguishable from monomania.

The chess-board is the world, the pieces are the phenomena of the universe, the rules of the game are what we call the laws of Nature. The player on the other side is hidden from us.

The dogma of the infallibility of the Bible is no more self-evident than is that of the infallibility of the popes.

The occurrence of successive forms of life upon our globe is an historical fact, which cannot be disputed; and the relation of these successive forms, as stages of evolution of the same type, is established in various cases.

The foundation of morality is to have done, once and for all, with lying.

Every living creature commences its existence under a form different from, and simpler than, that which it eventually attains.