Immanuel Kant

Synthetic judgments are those that add something to our knowledge.

The concept of duty is the foundation of all moral philosophy.

Ideas are the necessary conditions under which we are able to think about things.

The understanding does not derive its laws from, but imposes them upon, the objects of experience.

The critique of pure reason is a judgment of reason upon itself.

Freedom is the only condition under which a rational being can be the author of a law.

An action is morally good if it is done from duty, not merely in accordance with duty.

The principle of non-contradiction is the foundation of all logical reasoning.

Man is not merely a means to an end, but always at the same time an end.

Duty is the necessity to act out of reverence for the law.