When a thoughtful human being has overcome incentives to vice and is aware of having done his bitter duty, he finds himself in a state that could be called happiness, a state of contentment and peace of mind in which virtue is its own reward.

Every man is to be respected as an absolute end in himself; and it is a crime against the dignity that belongs to him as a human being, to use him as a mere means for some external purpose.

Man desired concord; but nature knows better what is good for his species; she desires discord. Man wants to live easy and content; but nature compels him to leave ease... and throw himself into roils and labors.

When I could have used a wife, I could not support one; and when I could support one, I no longer needed any

Philosophy stands in need of a science which shall determine the possibility, principles, and extent of human knowledge à priori.

He who is cruel to animals becomes hard also in his dealings with men. We can judge the heart of a man by his treatment of animals.

It is by his activities and not by enjoyment that man feels he is alive. In idleness we not only feel that life is fleeting, but we also feel lifeless.