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.

Act so that the maxim of your act could be made the principle of a universal law.

We assume a common sense as the necessary condition of the universal communicability of our knowledge, which is presupposed in every logic and every principle of knowledge that is not one of skepticism.

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.

The possession of power inevitably spoils the free use of reason.

The light dove, cleaving the air in her free flight, and feeling its resistance, might imagine that its flight would be still easier in empty space.

A society that is not willing to demand a life of somebody who has taken somebody else’s life is simply immoral.