Do not try to produce an ideal child, it would find no fitness in this world.

This survival of the fittest implies multiplication of the fittest.

All socialism involves slavery. That which fundamentally distinguishes the slave is that he labours under coercion to satisfy anothers desires.

In science the important thing is to modify and change one's ideas as science advances.

Agnostics are people who, like myself, confess themselves to be hopelessly ignorant concerning a variety of matters, about which metaphysicians and theologians, both orthodox and heterodox, dogmatize with the utmost confidence.

It must be admitted that the conception of virtue cannot be separated from the conception of happiness-producing conduct.

Life is not for learning nor is life for working, but learning and working are for life.