This essay proposes and defends a descriptive definition of morality. Under this definition, a moral system is a system of rules, psychological states, and modes of character development which performs the function of enabling mutually beneficial social cooperation. I shall argue that the methodologies employed by two prominent moral psychologists rely upon to establish a descriptive definition of morality only serve to track patterns in people's uses of moral terms. However, these methods at

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... st reveal a nominal definition of morality, since moral appraisers may be ignorant about the references of their moral terms. I propose a real definition of morality which characterizes moral systems as a natural kind-more precisely, a copied kind. I explain what it takes for a moral system to satisfy this definition, and I identify the sorts of evidence needed to distinguish moral systems from value systems of other kinds. 2