 In mentioning Newton’s speculation that an aether might explain universal gravity in some sense (for instance, in query 21 to the Opticks), Hume does not appear to be concerned about action at a distance; instead, he is concerned to argue that this speculation indicates that Newton himself did not regard his theory as requiring that we attribute a “power” of gravity to material bodies. This is important for Hume to establish, not least because he believes that we can form no representation at all of any such power. Similarly, when Newton indicates in the Principia that we can conceive of a body’s quantity of matter as its vis inertiae, its power of resisting any change to its state of motion (Newton 1999: 404–5), he is not attributing any power to that body, but rather employing a means of characterizing its behavior. Or so Hume contends. In this specific regard, we find an echo of Berkeley’s earlier work: in De Motu, Berkeley argues in particular that although some philosophers misunderstand the Newtonian theory of gravity as attributing a special force or nature to material objects, there is an interpretation of Newton that is consistent with the new theory of ideas. He writes (Berkeley 1992: De Motu, §6):