Some moral realists suggest that morality has progressed because some individuals recognized moral facts which are causally inert. I object causally inert facts, whether moral or mathematical, cannot serve as explanantia for anything, and then provide non-metaethical and moral antirealist explanations of why morality has progressed. I argue that moral antirealists, who aim to undermine the moral realist explanation, should provide a moral antirealist explanation rather than a non-metaethical explanation of why morality has progressed. I also point out that metaethical and non-metaethical explanations have respective limitations.