We can judge the heart of a man by his treatment of animals.

The infinitude of creation is great enough to make a world, or a Milky Way of worlds, look in comparison with it what a flower or an insect does in comparison with the Earth.

Enlightenment is man's emergence from his self-imposed immaturity...No thing is required for this enlightenment.. .except freedom; and the freedom in question is the least harmful of all, namely, the freedom to use reason publicly in all matters.

Act only according to that maxim whereby you can at the same time will that it should become a universal law.

There is no virtue in penance and fasting which waste the body; they are only fanatical and monkish.

Both love of mankind, and respect for their rights are duties; the former however is only a conditional, the latter an unconditional, purely imperative duty, which he must be perfectly certain not to have transgressed who would give himself up to the secret emotions arising from benevolence.

Procrastination is hardly more evil than grasping impatience.