Have the courage to use your own reason- That is the motto of enlightenment. "Foundations of the Metaphysics of Morals" (1785)

Men will not understand ... that when they fulfil their duties to men, they fulfil thereby God's commandments; that they are consequently always in the service of God, as long as their actions are moral, and that it is absolutely impossible to serve God otherwise.

What are the aims which are at the same time duties? They are perfecting of ourselves, the happiness of others.

Even a man's exact imitation of the song of the nightingale displeases us when we discover that it is a mimicry, and not the nightingale.

Human reason has this peculiar fate that in one species of its knowledge it is burdened by questions which, as prescribed by the very nature of reason itself, it is not able to ignore, but which, as transcending all its powers, it is also not able to answer.

Prudence approaches, conscience accuses.

What can I know? What ought I to do? What may I hope?