 This suggests that ethics, like mathematics, is an autonomous subject in the sense that it has its own “internal standards of justification and criticism”, such that its conclusions cannot be justified by other forms of inquiry such as evolutionary biology (Nagel 1979, 142; McDowell 1995 and 1997a,b). Normative ethical conclusions are justified through first-order ethical reflection and argument, just as mathematical propositions are justified through mathematical reasoning, rather than through learning more about our evolutionary past or about what is happening in our brains when we engage in these forms of reasoning (Rachels, 1990). It would seem to be as much of a mistake to try to answer ethical questions by examining fMRI scans or studying our evolutionary history as it would be to try to solve mathematical problems by such means (except, perhaps, insofar as evolutionary theory may shed light on some present, morally relevant empirical facts, as discussed below).