In every department of physical science there is only so much science, properly so-called, as there is mathematics.

[Aristotle formal logic thus far (1787)] has not been able to advance a single step, and hence is to all appearances closed and completed.

Genius is the ability to independently arrive at and understand concepts that would normally have to be taught by another person.

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!

Enlightenment is man's emergence from his self-incurred immaturity.

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

If we could see ourselves... as we really are, we should see ourselves in a world of spiritual natures, our community which neither began at birth nor will end with the death of the body.