 There is some question about just what Gould meant by the term ‘contingency’. Some philosophers read him as meaning that downstream outcomes are sensitive to small changes in upstream conditions (Ben-Menahem 1997; Inkpen &amp; Turner 2012). On this reading, contingency comes in degrees, and in contrast with historical insensitivity to changes in upstream conditions, which we could think of as historical convergence or robustness. When, for example, Sterelny (1995, crediting F. Jackson &amp; Pettit 1992) talks about “robust process explanations”, he means explanations that show how an outcome would have resulted from a wide range of upstream conditions.