All our knowledge falls with the bounds of experience. - Immanuel Kant

We can indeed recognize a tremendous difference in manner, but not in principle, between a shaman of the Tunguses and a European prelate: … for, as regards principle, they both belong to one and the same class, namely, the class of those who let their worship of God consist in what in itself can never make man better (in faith in certain statutory dogmas or celebration of certain arbitrary observances). Only those who mean to find the service of God solely in the disposition to good life-conduct distinguish themselves from those others, by virtue of having passed over to a wholly different principle.

From the crooked timber of humanity, a straight board cannot be hewn.

Mathematics, natural science, laws, arts, even morality, etc. do not completely fill the soul; there is always a space left over reserved for pure and speculative reason, the emptiness of which prompts us to seek in vagaries, buffooneries, and mysticism for what seems to be employment and entertainment, but what actually is mere pastime undertaken in order to deaden the troublesome voice of reason, which, in accordance with its nature, requires something that can satisfy it and does not merely subserve other ends or the interests of our inclinations.