 According Moore, all naturalistic analytic definitions of “good” fail, committing what he called “the naturalistic fallacy”. To show all naturalistic analyses of goodness fail, Moore presented the “open-question argument”. The basic idea is that if a definition of “good” is correct, a morally competent person could not sensibly question whether something satisfying the definition is good. Consider a definable term: a triangle is a closed plane figure with three angles. No person who understands the term can sensibly ask, “X is a triangle, but is X three-angled?” The question is closed; an open question is one it makes sense to ask. Moore claimed that for any naturalistic definition N of “good”, the question “X is N, but is it good?” is open. For example, suppose someone analyzes “good” as conducive to pleasure. If the analysis were correct, the question “X is conducive to pleasure, but is it good?” should be closed. But the question is open; it is perfectly reasonable. One might, e.g., think of schadenfreude—pleasure at another’s misfortune—and wonder whether such pleasure is good. Hence, Moore would conclude, the analysis fails. Moore held that the argument can be repeated for any proposed naturalistic analysis of “good”, so “good” cannot be analyzed in natural terms. He concluded that goodness is non-natural (see entry on  moral non-naturalism).  Moore went further, holding that “good” was unanalyzable, and that the property of goodness was simple and irreducible. These claims about goodness do not follow from the failure of all naturalistic analyses of “good”, since it might be possible to give a non-natural definition of “good”, e.g., as what God approves. However, although he does not seem to have recognized it, at least in Principia Ethica, the open question argument seems to work against nearly any definition of “good” just as it works against natural  definitions.[4]  (For more on the open question argument and objections to it, see the entry on  Moore’s Moral Philosophy.)