Galenic explanations in terms of capacities risk appearing circular; indeed, their post-Galenic descendants were famously mocked as such by Molière. Galen in fact admits openly that the statement that a substance or body “has an f-ic capacity” does not add anything to the statement that that substance or body “is capable of f-ing” (QAM 2, 377), even commenting that “we use the term ‘capacity’ when we do not know the substance (ousia!) of the active cause” (Nat. Fac. I.4).