Non-naturalist realists are committed to the belief, famously voiced by Parfit, that if there are no non-natural facts then nothing matters. But it is morally objectionable to conditionalise all our moral commitments on the question of whether there are non-natural facts. Non-natural facts are causally inefficacious, and so make no difference to the world of our experience. And to be a realist about such facts is to hold that they are mind-independent. It is compatible with our experiences that there are no non-natural facts, or that they are very different from what we think. As Nagel says, realism makes scepticism intelligible. So the non-naturalist must hold that you might be wrong that your partner matters, even if you are correct about every natural, causal fact about your history and relationship. But to hold that conditional attitude to your partner would be a moral betrayal. So believing non-naturalist realism involves doing something immoral.