Enlightenment is man's leaving his self-caused immaturity. Immaturity is the incapacity to use one's intelligence without the guidance of another. Such immaturity is self-caused if it is not caused by lack of intelligence, but by lack of determination and courage to use one's intelligence without being guided by another. Sapere Aude! Have the courage to use your own intelligence! is therefore the motto of the enlightenment.

From such crooked wood as that which man is made of, nothing straight can be fashioned.

The human heart refuses To believe in a universe Without a purpose.

Sincerity is the indispensable ground of all conscientiousness, and by consequence of all heartfelt religion.

If justice perishes, human life on Earth has lost its meaning.

Better the whole people perish than that injustice be done

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