Explicitly fictional armchair reconstructions of the past are sometimes taken to be informative about philosophical issues. What appeal a counterfactual genealogy has depends on its speculative accuracy, that is, its accuracy in identifying relevant causal, functional, or explanatory particulars. However, even when speculatively accurate, counterfactual genealogies rarely secure more than proofs of possibility. For more ambitious deployments of genealogy – for example, efforts to show what properties the target concept in fact predicates – genealogies are hamstrung by the possibility of (...) predicative drift, or changes over time in what the concept predicates. Still, even when counterfactual genealogies fail to tell us about our current practices or concepts, they may identify appealing successors. Pettit's (2018 Pettit, Philip. 2018. The Birth of Ethics: Reconstructing the Role and Nature of Morality. New York, NY: Oxford University Press.[Crossref], [Google Scholar]) innovative defense of moral realism and his employment of a counterfactual genealogy provides an illuminating instance of the promise and challenges facing accounts employing counterfactual genealogies. (shrink)