One of the more exciting things I'll be doing in the next few months is writing a paper for my class about moral realism. Moral realism is about more than rebutting relativism in ethics, as it is entirely possible to deny the objectivity or reality of morality without being a relativist about moral actions. David Hume for instance seems to have held this view. He believed that while the content of moral claims was expressive (essentially, referring to our emotions or feelings), nonetheless humans tend to have similar emotional responses to certain kinds of actions, thus making them "good" or "bad."
What we'll be focusing on instead is the ontological status of morality. Hume notwithstanding, most people seem to think that if morality is objective, then there must be some kind of reality to morality. But even if moral rules are real, they seem to be of a different kind than say, most physical objects.
It seems to me that there are a couple of main ways you might think of the reality of morality.
1) As Platonic or Moorean non-natural entities or properties.
2) As socially constructed relations between human actions and freedom, rationality, desires, actions, etc.
If you take morality to be referring to Platonic forms, it is easy to understand how these these entities are "real" enough to uphold claims of objectivity. The problem is that Platonic forms (or Moorean non-natural properties) are very odd things. I take it that Mackie's Argument from Queerness (that we shouldn't believe in the objectivity of moral claims because moral entities are unlike any other kind of entity) is primarily directed against this view.
If, however, you take moral claims to be referring to constructed relations then these entities no longer seem so strange. We are familiar with the reality of constructed relations such as marriage, games, art, etc. The problem is whether any socially constructed property, relation, et. al. will be strong enough to justify claims of objectivity in ethics. I assume that Mackie's Argument from Relativity (that the difference in moral codes makes it unlikely that they are the result of apprehending objective truths about morality) is meant to claim that it is not.
More on this later.
Politics, philosophy, religion, and other things