That G. E. Moore’s Principia Ethica has attained the status of a modern classic is amply attested by the number of references made to its central concepts and arguments. Moore’s central contention is that the adjective “good” refers to a simple, unique, and unanalyzable property. He claims that propositions containing value terms and ethical predicates are meaningful and can be found to be either true or false, even though the word “good” names an indefinable property knowable only by intuition or immediate insight. Moore also argues that the truth of propositions predicating intrinsic goodness—that is, that something is good on its own account, quite without reference to its value as a means—must likewise be seen immediately and without proof. The term “naturalistic fallacy” is proposed to name the error of mistaking some property other than goodness for goodness itself. Any definition of “good” would involve reference to something having distinguishable aspects or parts—hence, not simple; but since goodness is simple, any such definition would be false, an instance of the naturalistic fallacy.
The failure of previous systems of ethics, Moore alleges, is attributable to their imprecise formulations of the questions peculiar to ethics. His objective is to discover and lay down those basic principles according to which any scientific ethical investigation must proceed. Ethics should be concerned with two basic questions: “What kinds of things ought to exist for their own sakes?”—which presupposes knowledge of good—and “What kinds of actions ought we to perform?”
The first task of ethics, then, is to determine what “good” means. The only relevant type of definition is not a verbal definition but one that describes the real nature of what is denoted by stating the parts constituting the whole referent. However, in this sense of “definition,” “good” cannot be defined. It is a simple notion, not complex. The word “good,” like “yellow,” refers to an object of thought that is indefinable because it is one of many similarly ultimate terms presupposed by those complex ones that can be defined. True, one can give verbal equivalents of these notions; for example, yellow can be described in terms of light vibrations of certain frequencies—as the physicist might describe it—but light waves are obviously not identical with yellow as experienced. One either knows yellow in one’s experience or does not, for there is no substitute for the visual experience. Likewise, while there are other adjectives, such as “valuable,” that can be substituted for “good,” the property itself must be recognized in an act of direct insight.
With respect to the notion of good (as a property indicated by the adjective, not as a substantive, “a good” or “the good”), and to propositions predicating intrinsic goodness, Moore is an intuitionist. Such propositions are simply self-evident; proof is neither possible nor relevant. However, in other respects Moore rejects intuitionism; he denies that such propositions are true because they are known by intuition. Holding that this, like any other way of cognizing, may be mistaken, he also denies that propositions in answer to the second basic question—concerning what ought to be done—can be known intuitively, since it is a question of means involving intricate causal relations and variable conditions and circumstances. Judgments about intrinsic goodness are true universally if true at all, but in order to know what one ought to do, that is, to know that any given action is the best, one would have to know that the anticipated effects are always produced and that the totality of these reflect a balance of good superior to that of any alternatives. Such judgments can be only probable, never certain. Thus, both types of ethical judgment presuppose the notion of good but in ways not always clearly distinguished. The situation is complicated because various...
(The entire section is 3,599 words.)