All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.

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

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

But a lie is a lie, and in itself intrinsically evil, whether it be told with good or bad intents.

We can judge the heart of a man by his treatment of animals.

The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a principle of reason; by the latter one necessarily shunned, also according to a principle of reason.

If education is to develop human nature so that it may attain the object of its being, it must involve the exercise of judgment.