 Consider type recursions next. Suppose we must know actual reproduction rates to assign relative fitnesses values in type recursions. Were this so, an alleged explanation of the extent of evolutionary change in the system that makes crucial use of type recursions would be circular. The circularity problem does not come up for practicing biologists deploying type recursions, as those workers rely upon fitness estimates that are inferred from statistical facts about a target system during the estimation phase in order to assign values to variables in type recursions that are then deployed over the system during the projection phase. What such biologists mean to explain, the behavior during the projection phase, is different from what they use to construct the explanation, the behavior during the estimation phase (Mills &amp; Beatty 1979; Bouchard &amp; Rosenberg 2004; the estimation/projection phase contrast is due to Glymour 2006).