The classical conceptions regarded theory as superior to practice because theory embodied the goal of man as a rational being. Kant took the ethical, practical sphere to be superior to the sphere of knowledge because in those contents with which it deals the latter is unable to decide whether or not beings denoted by these contents exist. The decision in favor of the existence of these contents come from ethical and not cognitive sources. Both the classical and the Kantian conceptions show a preference of one sphere as over against the other. Our purpose here shall be to indicate the primacy of the theoretical sphere with respect to the practical — a primacy that in no way entails a preference or superiority of theory over practice — and then show that there is no meaning to significant decisions in the practical sphere without first assuming such decisions in the theoretical.