The only method compatible with our notions of civilization and the race is to prevent the breeding of the unfit by sterilization and the deliberate guidance of the mating instinct. [...] The trend of opinion among eugenists is that we must make marriage more difficult. Certainly no one who is not a desirable parent should be permitted to produce progeny.

You may live to see man-made horrors beyond your comprehension.

I am credited with being one of the hardest workers and perhaps I am, if thought is the equivalent of labour, for I have devoted to it almost all of my waking hours. But if work is interpreted to be a definite performance in a specified time according to a rigid rule, then I may be the worst of idlers.

So we find that the three possible solutions of the great problem of increasing human energy are answered by the three words: food, peace, work... Their scientific meaning and purpose now clear to me: food to increase the mass, peace to diminish the retarding force, and work to increase the force accelerating human movement.

Sometimes I feel that by not marrying, I made too great a sacrifice to my work.

Religion is simply an ideal. It is an ideal force that tends to free the human being from material bonds. I do not believe that matter and energy are interchangeable, any more than are the body and soul. There is just so much matter in the universe and it cannot be destroyed. As I see life on this planet, there is no individuality. It may sound ridiculous to say so, but I believe each person is but a wave passing through space, ever-changing from minute to minute as it travels along, finally, some day, just becoming dissolved.

Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality.