I say quite deliberately that the Christian religion, as organized in its Churches, has been and still is the principal enemy of moral progress in the world.

Descartes, the father of modern philosophy ... would never-so he assures us-have been led to construct his philosophy if he had had only one teacher, for then he would have believed what he had been told; but, finding that his professors disagreed with each other, he was forced to conclude that no existing doctrine was certain.

Ethical metaphysics is fundamentally an attempt, however disguised, to give legislative force to our own wishes.

Politics is largely governed by sententious platitudes which are devoid of truth

What will be the good of the conquest of leisure and health, if no one remembers how to use them?

Love should be a tree whose roots are deep in the earth, but whose branches extend into heaven.

Love cannot exists as a duty; to tell a child that it ought to love its parents and its brother and sisters is utterly useless, if not worse.