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

I believe four ingredients are necessary for happiness: health, warm personal relations, sufficient means to keep you from want, and successful work.

Broadly speaking, Protestants like to be good and have invented theology in order to keep themselves so, whereas Catholics like to be bad and have invented theology in order to keep their neighbors good. Hence, the social character of Catholicism and the individual character of Protestantism.

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

Moreover, the attitude that one ought to believe such and such a proposition, independently of the question whether there is evidence in its favor, is an attitude which produces hostility to evidence and causes us to close our minds to every fact that does not suit our prejudices.

What the world needs is not dogma but an attitude of scientific inquiry.

There is as much difference between a collection of mentally free citizens and a community molded by modern methods of propaganda as there is between a heap of raw materials and a battleship.