Dogmatism is the greatest of mental obstacles to human happiness.

The fundamental concept in social science is Power, in the same sense in which Energy is the fundamental concept in physics.

Machines are worshipped because they are beautiful and valued because they confer power; they are hated because they are hideous and loathed because they impose slavery.

I do not think any reasonable person can doubt that in India, China and Japan, if the knowledge of birth control existed, the birthrate would fall very rapidly

A good world needs knowledge, kindliness, and courage; it does not need a regretful hankering after the past or a fettering of the free intelligence by the words uttered long ago by ignorant men.

There may be no good reasons for very many opinions that are held with passion.

One of the most painful circumstances of recent advances in science is that each one makes us know less than we thought we did