 Many of Kant’s commentators, who are skeptical about these apparently exorbitant metaphysical claims, have attempted to make sense of his discussions of the intelligible and sensible worlds in less metaphysically demanding ways. On one interpretation (Hudson 1994), one and the same act can be described in wholly physical terms (as an appearance) and also in irreducibly mental terms (as a thing in itself). On this compatibilist picture, all acts are causally determined, but a free act is one that can be described as determined by irreducibly mental causes, and in particular by the causality of reason. A second interpretation holds that the intelligible and sensible worlds are used as metaphors for two ways of conceiving of one and the same world (Korsgaard 1996; Allison 1990; Hill 1989a, 1989b). When we are engaging in scientific or empirical investigations, we often take up a perspective in which we think of things as subject to natural causation, but when we deliberate, act, reason and judge, we often take up a different perspective, in which we think of ourselves and others as agents who are not determined by natural causes. When we take up this latter, practical, standpoint, we need not believe that we or others really are free, in any deep metaphysical sense; we need only operate “under the idea of freedom” (G 4:448). Controversy persists, however, about whether Kant’s conception of freedom requires a “two worlds” or “two perspectives” account of the sensible and intelligible worlds (Guyer 1987, 2009; Langton 2001; Kohl 2016; Wood 1984; Hogan 2009).