How to prove that some acts are wrong (without using substantive moral premises)

I first argue that there are many true claims of the form: Φ-ing would be morally required, if anything is. I then explain why the following conditional-type is true: If φ-ing would be morally required, if anything is, then anything is actually morally required. These results allow us to construct valid proofs for the existence of some substantive moral facts—proofs that some particular acts really are morally required. Most importantly, none of my argumentation presupposes any substantive moral claim; I use only plausible claims that most moral skeptics and error theorists can and do accept. The final section diagnoses why my arguments work. Here, I offer an explanation for the supervenience of the moral on the non-moral that may help those worried that the strategy is a sophisticated trick. I conclude by considering two objections. In replying to these objections, I explain why the strategy may allow us to demonstrate more than “obvious” moral truths, and why it may also address a stronger version of error theory, according to which, moral truths are not possible.