First I would like to thank Dan Garber for setting forth an extremely bold and fresh thesis on a central issue of Cartesian interpretation. It is not often that someone dares to offer a new resolution to a problem that has been tackled variously, for the last three centuries, by all the great Cartesians and their interpreters. Garber's thesis pits itself directly against the standard line initiated by Descartes” closest disciples and perpetuated by most commentators. Moreover, in order to resolve an alleged inconsistency among some basic Cartesian principles, the thesis also takes issue with some of Descartes” statements themselves, and attempts to correct Descartes, using some deeply entrenched Cartesian principles against what seem to be less deeply entrenched principles. I wish to support Garber's rejection of the standard Cartesian interpretations concerning the intelligibility of mind-body interactions, but I shall argue that Descartes would not have accepted Garber's suggestion relative to the resolution of the problem because Descartes would not have considered the alleged inconsistency among his principles as real. The great Cartesians all shared Elizabeth's puzzlement about how to understand an interaction between an immaterial substance and an extended substance. So Elizabeth accomplished a service to the future philosophical community when she requested an explanation from Descartes concerning this problem; she naturally formulated the request as an explanation of the interaction between mind and body in terms of the reputedly less puzzling interaction between bodies. But Descartes rejected Elizabeth's request by invoking his principle of the primitive notions (here, the primitive notions are extension, thought, and the union). According to Descartes, any attempt to explain one of these primitive notions by means of the other is doomed to failure in advance, since “all human science consists solely in clearly distinguishing these notions and attaching each of them only to the things to which it applies."? Hence, any attempt to explain mind-body interaction in terms of body-body interaction would be to explain what is proper to the union in terms of what is proper to extension. But–and this is simply the other side of the same coin–any attempt to explain bodybody interaction in terms of mind-body interaction would be to explain what is proper to extension alone in terms of what is proper to the union; this, of course, according to Descartes, is the error committed by the physicists of substantial form. As Garber points out, Descartes' example concerning the Scholastic analysis of heaviness makes this point extremely well: for the Scholastics, a body is heavy because it