APA Dictionary of Psychology

the position, stated definitively by Greek philosopher Plato (c. 427–c. 347 bce), that one who knows the good will (necessarily) do the good. It is implied that a sense of obligation is the defining feature of knowledge of the good and that this sense will be strong enough to compel, rather than merely suggest, action. This position assumes the essential rationality of human beings. Later modifications of the position have argued that a person will necessarily act in accordance with what they perceive to be good, whether or not it really is good, or that a person will act consistently with what they perceive to be good, where what is good is what is in that person’s self-interest (see eudemonism). Also called moral determinism.