Immaturity is the incapacity to use one's intelligence without the guidance of another.

That Logic has advanced in this sure course, even from the earliest times, is apparent from the fact that, since Aristotle, it has been unable to advance a step, and thus to all appearance has reached its completion.

It is often necessary to make a decision on the basis of knowledge sufficient for action but insufficient to satisfy the intellect.

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

[S]uppose the mind of [a] friend of humanity were clouded over with his own grief, extinguishing all sympathetic participation in the fate of others; he still has the resources to be beneficent to those suffering distress, but the distress of others does not touch him because he is sufficiently busy with his own; and now, where no inclination any longer stimulates him to it, he tears himself out of his deadly insensibility and does the action without any inclination, solely from duty.

[A ruler is merely] the trustee of the rights of other men and he must always stand in dread of having in some way violated these rights.

Melancholy characterizes those with a superb sense of the sublime.