Adviser: Professor Stefan Baumrin In the first chapter I introduce the distinction between metaethics and normative ethics and argue that metaethics, properly conceived, is a part of cognitive science. For example, the debate between rationalism and sentimentalism can be informed by recent empirical work in psychology and the neurosciences. In the second chapter I argue that the traditional view that one’s theory of semantics determines what one’s theory of justification must be is mistaken. Though it has been the case that (...) there are ‘typical’ combinations of semantic and justificational theories this is by no means forced on one. In the third chapter I examine two current kinds of expressivism; that of Blackburn and Copp. Each gives us an example of different combinations of semantic and justificatory theory. In Blackburn’s case he combines a use theory of meaning with a classic emotivist theory of justification, In Copp’s case it is a neo-Gricean philosophy of language with a realist’s theory of justification. I find both of these wanting as they ultimately collapse into relativistic subjectivism. In the fourth and fifth chapter I turn to developing Emotive Realism. The basic idea behind this view is that when someone says ‘x is wrong/right’ that person has (a) expressed a moral emotion about x and at the same time (b) expressed the belief that the emotion in (a) is the correct one to have. The belief expressed in (b) will be true or false depending on one’s theory of justification. In the fourth chapter I argue that we need separate semantic theories for thoughts and sentences. In the fifth chapter I fill in the details of Emotive Realism as I see it. (shrink)