The open-question argument claims that any attempt to identify morality with some set of observable, natural properties will always be liable to an open question, and that if this is true, then moral facts cannot be reduced to natural properties and that therefore ethical naturalism is false. Put another way, Moore is saying that any attempt to define good in terms of a natural property fails because such definitions can be transformed into closed questions (the subject and predicate being conceptually identical, that is, the two terms mean the same thing); however, all purported naturalistic definitions of good are transformable into open questions, for it can still be questioned whether good is the same thing as pleasure, etc. Shortly before (in section §11), Moore had said if good is defined as pleasure, or any other natural property, "good" may be substituted for "pleasure", or that other property, anywhere where it occurs. However, "pleasure is good" is a meaningful, informative statement; but "good is good" (after making the substitution) is an uninformative tautology.