  These arguments for moral skepticism differ in many ways, but they seem mutually supportive. One crucial premise in the skeptical hypothesis argument claims that nothing can rule out moral nihilism. The best way to support that premise is to criticize each method for ruling out moral nihilism. That is just one instance of what the regress argument does more generally. The argument from moral explanations excludes yet another way to rule out moral nihilism. So, if these other arguments work, they support a crucial premise in the skeptical hypothesis argument.