All human knowledge begins with intuitions, proceeds from thence to concepts, and ends with ideas.

Upon the solution of this problem, or upon sufficient proof of the impossibility of synthetical knowledge a priori, depends the existence or downfall of metaphysics.

I am an investigator by inclination. I feel a great thirst for knowledge.

Freedom can never be comprehended, nor even can insight into it be gained.

The science of mathematics presents the most brilliant example of how pure reason may successfully enlarge its domain without the aid of experience

Two things awe me most, the starry sky above me and the moral law within me.

If we knew that god exists, such knowledge would make morality impossible. For, if we acted morally from fear or fright, or confident of a reward, then this would not be moral. It would be enlightened selfishness.