Contemporary moral realists assume that goodness is a property susceptible to Kripkean/Putnamian developments in philosophy of language and metaphysics. However, close attention to the actual use of the term 'good' reveals that 'good' does not refer to a property but to a predicate-forming functor. Relying on an argument advanced by P.T. Geach, I argue that the semantics of 'good' is such that statements of the form "x is good" are semantically incomplete. In order to complete such statements some substantive has to be understood. I go on to argue that the semantics of 'good' has profound implications for metaethics. First, I show that goodness is not a property capable of figuring into necessary a posteriori identities. Thus, most contemporary defenses of moral realism fail. Second, I show that the semantics of 'good' reveals that 'good' must modify something that has a nature and function. I go on to argue that if it is true that 'good' must modify something that has a nature and function, then human goodness is both unique and uniform. Human goodness is unique because human nature is. Human goodness is uniform because human nature is. Third, I show that the correct metaphysics for functions is a normative account that supports the semantics of 'good' provided earlier. In the process of defending a normative account of functions I show that theories of functions that rely solely on evolutionary theory fail. Lastly, I consider and respond to some standard objections to moral realism. In particular, I examine the argument from motivation, the argument from queerness and the argument from the supervenience of the moral on the non-moral. I show that the metaethical theory that emerged in the first three parts of the dissertation easily handles each of these arguments.