Always recognize that human individuals are ends, and do not use them as means to your end.

Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end, but always at the same time as an end.

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

An age cannot bind itself and ordain to put the succeeding one into such a condition that it cannot extend its (at best very occasional) knowledge , purify itself of errors, and progress in general enlightenment. That would be a crime against human nature, the proper destination of which lies precisely in this progress and the descendants would be fully justified in rejecting those decrees as having been made in an unwarranted and malicious manner.

The touchstone of everything that can be concluded as a law for a people lies in the question whether the people could have imposed such a law on itself.

Live your life as though your every act were to become a universal law.

Means we use must be as pure as the ends we seek.