To behold virtue in her proper form is nothing else but to contemplate morality stripped of all admixture of sensible things and of every spurious or… - Immanuel Kant

Philosophical knowledge is the knowledge gained by reason from concepts; mathematical knowledge is the knowledge gained by reason from the construction of concepts.

"A good will is good not because of what it effects, or accomplishes, not because of its fitness to attain some intended end, but good just by its willing, i.e. in itself; and, considered by itself, it is to be esteemed beyond compare much higher than anything that could ever be brought about by it in favor of some inclinations, and indeed, if you will, the sum of all inclinations. Even if by some particular disfavor of fate, or by the scanty endowment of a stepmotherly nature, this will should entirely lack the capacity to carry through its purpose; if despite its greatest striving it should still accomplish nothing, and only the good will were to remain (not of course, as a mere wish, but as the summoning of all means that are within our control); then, like a jewel, it would still shine by itself, as something that has full worth in itself".

By a lie a man throws away, and as it were, annihilates his dignity as a man.