mathematical conceptions and theorems. Thus, X (i.e. some non-moral property) might well be analytically equivalent to the good, and still the question of "Is X good?" can be meaningful. Ergo premise 1 does not hold and the argument falls. Frege sense–reference distinction Sense and reference are two different aspects of some terms' meanings. A term's reference is the object to which the term refers, while the term's sense is the way that the term refers to that object. There is a difference between the sense of a term and its reference (i.e. the object itself). Thus, we can understand a claim like "goodness is identical with pleasure" as an a posteriori identity claim similar to "Water is H2O". The question "This is H2O but is it water?" is intelligible and so, in that limited sense, whether or not water is H2O is an open question; note that this does not address the issue of significance. But that does not lead us to conclude that water is not H2O. "Water is H2O" is an identity claim that is known to be true a posteriori (i.e., it was discovered via empirical investigation). Another example is "redness" being identical to certain phenomena of electromagnetism. This is discovered by empirical investigation. Similarly, many moral naturalists argue that "rightness" can be discovered as an a posteriori truth, by investigating the different claims, like that of pleasure being the good, or of duty being the good. This is done by invoking rightness and wrongness to explain certain empirical phenomena, and then discovering a posteriori whether maximizing utility occupies the relevant explanatory role. For example, they argue that since right actions contingently have certain effects e.g. being causally responsible for a tendency towards social stability—so it follows we can fix the term "right" refer to the empirical description "the property of acts, whatever it is, that is causally responsible for their tendency towards social stability." With this description for "right," we can then investigate which acts accomplish this: e.g. those actions that maximize utility. We can then conclude that we have learned that "right" refers to "maximizing utility" through a posteriori means. The Frege sense–reference distinction can be understood in layman's terms by using the analogy of the Masked Man. A citizen living on the frontiers of the Wild West is told by the sheriff that his brother is the Masked Man who has recently been robbing