Human freedom is realised in the adoption of humanity as an end in itself, for the one thing that no-one can be compelled to do by another is to adopt a particular end. - 'Metaphysical Principles of Virtue
The history of the human race, viewed as a whole, may be regarded as the realization of a hidden plan of nature to bring about a political constitution, internally, and for this purpose, also externally perfect, as the only state in which all the capacities implanted by her in mankind can be fully developed.
Enlightenment is man's emergence from his self-imposed nonage. Nonage is the inability to use one's own understanding without another's guidance. This nonage is self-imposed if its cause lies not in lack of understanding but in indecision and lack of courage to use one's own mind without another's guidance. Dare to know!
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 means employed by Nature to bring about the development of all the capacities of men is their antagonism in society, so far as this is, in the end, the cause of a lawful order among men.
Philosophical knowledge is the knowledge gained by reason from concepts ; mathematical knowledge is the knowledge gained by reason from the construction of concepts.