The population question is the real riddle of the sphinx, to which no political Oedipus has as yet found the answer. In view of the ravages of the terrible monster over-multiplication, all other riddle sink into insignificance.

Irrationally held truths may be more harmful than reasoned errors.

A drop of water is as powerful as a thunder-bolt.

The birth of science was the death of superstition.

I take it that the good of mankind means the attainment, by every man, of all the happiness which he can enjoy without diminishing the happiness of his fellow men

A world of facts lies outside and beyond the world of words.

Science is nothing, but trained and organized common sense.