Always recognize that human individuals are ends, and do not use them as means to your end.

It is often necessary to make a decision on the basis of knowledge sufficient for action but insufficient to satisfy the intellect.

Out of the crooked timber of humanity, no straight thing was ever made.

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

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.

Everything in nature acts in conformity with law.

Thoughts without content are empty, intuitions without concepts are blind.