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.

I conceive that the leading characteristic of the nineteenth century has been the rapid growth of the scientific spirit, the consequent application of scientific methods of investigation to all the problems with which the human mind is occupied, and the correlative rejection of traditional beliefs which have proved their incompetence to bear such investigation.

There is no sea more dangerous than the ocean of practical politics none in which there is more need of good pilotage and of a single, unfaltering purpose when the waves rise high.

The foundation of all morality is to have done, once and for all, with lying; to give up pretending to believe that for which there is no evidence, and repeating unintelligible propositions about things beyond the possibilities of knowledge.

The man of science has learned to believe in justification, not by faith, but by verification.

Science commits suicide when it adopts a creed.

The man who is all morality and intellect, although he may be good and even great, is, after all, only half a man.