 This entry will briefly introduce eight kinds of theory. Be aware, that these will be merely sketches of the basic ideas. Note also that the theories are not all intended as examples of reductive normative naturalistic realism. In some cases, the intention is merely to illuminate the nature of normativity without achieving a constitutive explanation of normativity. Some of the examples are realist, but some are anti-realist, expressivist or constructivist. And among the realist cases are examples of both mind-independent normative realism and of basic normative realism. We begin with a perspective on the nature of normativity that has been taken to support non-cognitivist expressivism, although it can also be interpreted in a way that is friendly to realism. We then sketch two ideas that are examples of basic-realist approaches, but that eschew mind-independence. They are sometimes classified as “constructivist” and anti-realist. It is not until we reach the final two cases, in  section 4.7  and  section 4.8,  that we find clear examples of naturalistic constitutive explanations of robust normativity that are also examples of mind-independent realism. What follows, then, are eight strategies that have been used in attempting to explain normativity.