 As we saw at the beginning of this entry, some of the earliest thinking in empirically-informed moral philosophy concerns moral disagreement. Brandt and Ladd conducted in-depth investigations into the moral codes of other groups, and some contemporary moral philosophers have argued for continuing attention to the empirical details of moral disagreement. This is partly due to the influence of Mackie’s (1977: 36–37) formulation of what he dubbed ‘the argument from relativity’ in terms of an inference to the best explanation: the best explanation of the nature and persistence of moral diversity, Mackie argues, is that our moral judgments represent “ways of life,” rather than “perceptions, most of them seriously inadequate and badly distorted, of objective moral values.” Realists have tended to respond to the argument by pointing to other possible explanations of disagreement that are consistent with objectivity, such as mistakes about the non-moral facts, irrationality, and failures of impartiality and imagination (e.g., Brink 1984; Sturgeon 1988; Smith 1994; Shafer-Landau 2003; for an overview and analysis of realist responses, see Loeb 1998).