The hand is the visible part of the brain. - Immanuel Kant

Nobody can claim himself to be practically proficient in a science and yet disdain its theory without revealing himself to be an ignoramus in his area.

Criticism alone can sever the root of materialism, fatalism, atheism, free-thinking, fanaticism, and superstition, which can be injurious universally; as well as of idealism and skepticism, which are dangerous chiefly to the Schools, and hardly allow of being handed on to the public.

That religion in which I must know in advance that something is a divine command in order to recognize it as my duty, is the revealed religion (or the one standing in need of a revelation); in contrast, that religion in which I must first know that something is my duty before I can accept it as a divine injunction is the natural religion. … When religion is classified not with reference to its first origin and its inner possibility (here it is divided into natural and revealed religion) but with respect to its characteristics which make it capable of being shared widely with others, it can be of two kinds: either the natural religion, of which (once it has arisen) everyone can be convinced through his own reason, or a learned religion, of which one can convince others only through the agency of learning (in and through which they must be guided). … A religion, accordingly, can be natural, and at the same time revealed, when it is so constituted that men could and ought to have discovered it of themselves merely through the use of their reason, although they would not have come upon it so early, or over so wide an area, as is required. Hence a revelation thereof at a given time and in a given place might well be wise and very advantageous to the human race, in that, when once the religion thus introduced is here, and has been made known publicly, everyone can henceforth by himself and with his own reason convince himself of its truth. In this event the religion is objectively a natural religion, though subjectively one that has been revealed.