Science is simply common sense at its best, that is, rigidly accurate in observation, and merciless to fallacy in logic.

Social progress means a checking of the cosmic process at every step and the substitution for it of another, which may be called the ethical process; the end of which is not the survival of those who may happen to be the fittest, in respect of the whole of the conditions which obtain, but of those who are ethically the best.

Missionaries, whether of philosophy or religion, rarely make rapid way, unless their preachings fall in with the prepossessions ofthe multitude of shallow thinkers, or can be made to serve as a stalking-horse for the promotion of the practical aims of the still larger multitude, who do not profess to think much, but are quite certain they want a great deal.

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

The ultimate court of appeal is observation and experiment... not authority.

Genius, as an explosive power, beats gunpowder hollow.

I am too much of a sceptic to deny the possibility of anything...