One of the main causes of trouble in the world is dogmatic and fanatical belief in some doctrine for which there is no adequate evidence

But courage in fighting is by no means the only form, nor perhaps even the most important. There is courage in facing poverty, courage in facing derision, courage in facing the hostility of one's own herd. In these, the bravest soldiers are often lamentably deficient. And above all there is the courage to think calmly and rationally in the face of danger, and to control the impulse of panic fear or panic rage.

Science tells us what we can know but what we can know is little and if we forget how much we cannot know we become insensitive of many things of very great importance. Theology, on the other hand induces a dogmatic belief that we have knowledge where in fact we have ignorance and by doing so generates a kind of impertinent insolence towards the universe. Uncertainty in the presence of vivid hopes and fears is painful, but must be endured if we wish to live without the support of comforting fairy tales.

Ethical metaphysics is fundamentally an attempt, however disguised, to give legislative force to our own wishes.

If a Black Death could be spread throughout the world once in every generation survivors could procreate freely without making the world too full.

Mathematics, rightly viewed, possesses not only truth, but supreme beauty-a beauty cold and austere ... yet sublimely pure and capable of stern perfection such as only the greatest art can show.

It is only through imagination that men become aware of what the world might be; without it, ‘progress’ would become mechanical and trivial.