All religion is slavery.

Mental slavery is mental death, and every man who has given up his intellectual freedom is the living coffin of his dead soul.

Every cradle asks us, Whence? and every coffin, Whither? The poor barbarian, weeping above his dead, can answer these questions as intelligently as the robed priest of the most authentic creed.

What light is to the eyes - what air is to the lungs - what love is to the heart, liberty is to the soul of man.

If all the historic books of the Bible were blotted from the memory of mankind, nothing of value would be lost.

[T]he blossom of benevolence, of charity, is the fairest flower, no matter whether it blooms by the side of a hovel, or bursts from a vine climbing the marble pillar of a palace. I respect no man because he is rich; I hold in contempt no man because he is poor.

Only a few years ago there was no person too ignorant to successfully answer Charles Darwin; and the more ignorant he was the more cheerfully he undertook the task.