I cannot favour laws such as that of Idaho, which allows sterilization of 'mental defectives, epileptics, habitual criminals, moral degenerates, and sex perverts.' The last two categories here are very vague . . . The law of Idaho would have justified the sterilization of Socrates, Plato, Julius Caesar, and St. Paul.

When there are rational grounds for an opinion, people are content to set them forth and wait for them to operate. In such cases, people do not hold their opinions with passion; they hold them calmly, and set forth their reasons quietly. The opinions that are held with passion are always those for which no good ground exists; indeed the passion is the measure of the holder's lack of rational conviction.

We ought to look the world frankly in the face.

Thought is subversive and revolutionary, destructive and terrible, Thought is merciless to privilege, established institutions, and comfortable habit. Thought is great and swift and free.

I am sometimes shocked by the blasphemies of those who think themselves pious.

The true spirit of delight, the exaltation, the sense of being more than Man, which is the touchstone of the highest excellence, is to be found in mathematics as surely as poetry.

True happiness for human beings is possible only to those who develop their godlike potentialities to the utmost.