 A rare case of Kantian irony, it seems. Already in this early text, Kant has clearly broken with his predecessors both in England and on the Continent, who insisted on disputing Newton’s theory of universal gravity, either on metaphysical or theological grounds. Instead, Kant’s work will be predicated on that theory. But Kant never became an orthodox Newtonian, any more than an orthodox Leibnizian (or Wolffian). This is evident from the radically different fates of two classic Newtonian concepts within the Kantian system: the idea that the theory of universal gravity shows that gravity is a feature of material bodies, along with the related concept of action at a distance, on the one hand; and absolute space, on the other. The quotation from 1763 above indicates that Kant was willing to endorse Newton’s theory of universal gravity, despite the many objections raised against it by his Leibnizian predecessors. Indeed, he was also willing to accept the most radical interpretation of that theory, one according to which every material body in the world should be understood as bearing a feature called gravity, one that involves that body in actions at a distance on all other such bodies. As Kant puts it dramatically in Proposition 7 of the second chapter of Metaphysical Foundations of Natural Science: “The attraction essential to all matter is an immediate action of matter on other matter through empty space” (Kant 1786 [2002: 223]; AK 4: 512). This view is radical in two senses: first, it involves the highly controversial claim that gravity is essential to matter, which indicates that a body lacking gravitational interactions would potentially fail to count as a material entity at all (much as an earlier generation of philosophers would conceive of extension as essential to matter); and second, it also involves the debated idea that material bodies act at a distance on one another. One can conceivably endorse the latter without endorsing the former, contending, e.g., that although material bodies in the actual world act at a distance on one another, perhaps because of a divine plan, it is perfectly possible for material bodies to fail to do so under distinct worldly conditions (i.e., there may be possible worlds in which material bodies lack gravity altogether). That is, the endorsement of action at a distance does not entail the endorsement of the essentiality claim. Both ideas are controversial, and Kant strongly endorses them both. This placed him in a rather select group of radical Newtonians (Friedman 1992: 1 note 2). Kant himself understood that Newton may not have endorsed these controversial views, arguing that he was inconsistent on this score (see Remark 2 to Proposition 7 of chapter 2, AK 4: 514–16; Friedman 2012: 203–21). And yet Kant strongly resisted the other most controversial Newtonian idea, absolute space, along with the related idea of absolute motion (Friedman 2012: 35–42). In the Critique of Pure Reason, for instance, Kant expressed a basically Leibnizian sympathy by arguing that there are fundamental metaphysical (and perhaps epistemic) difficulties with thinking of space and time as existing independently of all objects and all possible relations among them as “actual entities ”(wirkliche Wesen—A23/B37) in their own right. He does so in a passage that (perhaps confusingly) characterizes the Leibnizians as also defending a kind of realism about space, but we can focus solely on his criticism of the Newtonians: