Our knowledge springs from two fundamental sources of the mind; the first is the capacity of receiving representations (receptivity for impressions), the second is the power of knowing an object through these representations (spontaneity [in the production] of concepts).

Reason must approach nature in order to be taught by it. It must not, however, do so in the character of a pupil who listens to everything that the teacher chooses to say, but of an appointed judge who compels the witness to answer questions which he has himself formulated.

The business of philosophy is not to give rules, but to analyze the private judgments of common reason.

The death of dogma is the birth of morality.

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

Act so that the maxim of your act could be made the principle of a universal law.

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