This document discusses different theories of moral realism and anti-realism. It presents the views of moral realism, which claims that objective moral facts exist independently of human beliefs and attitudes. It also discusses anti-realism and skepticism, which reject or are uncertain about the existence of objective moral truths. The document then examines arguments from relativity and queerness against moral realism, before analyzing radical moral nihilism and J.L. Mackie's defense of that view.