Only the descent into the hell of self-knowledge can pave the way to godliness. - Immanuel Kant

That all our knowledge begins with experience there can be no doubt. For how is it possible that the faculty of cognition should be awakened into exercise otherwise than by means of objects which affect our senses, and partly of them selves produce representations, partly rouse our powers of understanding into activity, to compare, to connect, or to separate these, and so to convert the raw material of our sensuous impressions into a knowledge of objects, which is called experience? In respect of time, therefore, no knowledge of ours is antecedent to experience, but begins with it. But though all our knowledge begins with experience, it by no means follows, that all arises out of experience. For, on the contrary, it is quite possible that our empirical knowledge is a compound of that which we receive through impressions, and that which the faculty of cognition supplies from itself (sensuous impressions giving merely the occasion)... It is, therefore, a question which requires close investigation, and is not to be answered at first sight,—whether there exists a knowledge altogether independent of experience, and even of all sensuous impressions? Knowledge of this kind is called à priori, in contradistinction to empirical knowledge which has its sources à posteriori, that is, in experience.

"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".

...[T]he sublimity and intrinsic dignity of the command in duty are so much the more evident, the less the subjective impulses favor it and the more they oppose it, without being able in the slightest degree to weaken the obligation of the law or to diminish its validity.