Featured Term (selected at random):NOUMENON The essence of a thing. In Kantian philosophy the mind can only postulate but never know the essence of things. The essence of God, the soul, the moral law, and anything else thus become suppositions of practical reason, and people are to act on these presuppositions "as if" they really existed. This makes life livable. (Etym. Greek nooumenon, that which is apprehended by thought.) All items in this dictionary are from Fr. John Hardon's Modern Catholic Dictionary, © Eternal Life. Used with permission.