The most prominent controversy in Hume scholarship over the last couple of decades has been the socalled “New Hume” debate, concerning whether or not Hume is a realist about Causal powers (the capitalised term signifying a “thick” connexion that goes beyond his famous two “definitions of cause”).1 The long-familiar “Old Hume” takes very seriously his “Copy Principle” (in Treatise 1.1.1 and Enquiry 2) that all simple ideas are copies of impressions, from which they derive both their existence and their significance. Our thoughts are confined within the scope of our ideas, and hence any coherent thought must ultimately be constituted entirely by impression-copy content. But Hume’s search for the source of our idea of power or necessary connexion (in Treatise 1.3.14 and Enquiry 7) notoriously reveals it as being copied from a subjective impression – a feeling, or perhaps more precisely a reflexive awareness,2 of making customary inferences in response to observed constant conjunctions. Such an idea cannot possibly represent coherently any objective thick connexion, and so this Old Hume position denies even the coherence of any would-be thought about such connexions: the question of their real existence, therefore, cannot even arise. Causation is reduced to being a matter of regularity or “constant conjunction”, together with the accompanying tendency of the mind to draw inferences accordingly. But exactly how these two elements – and the two definitions that capture them – are supposed to combine together in yielding a single “idea of necessary connexion” is far from clear. So it is not surprising that a variety of Old Humean readings have been proposed, ranging from straightforward regularity reductionism to subtle forms of “projectivism” or “quasirealism”.3 What they all have in common, and what sharply distinguishes them from the various New Humean interpretations, is their denial that causal necessity involves any objective “thick” connexion. For the Old Hume, causal necessity in the objects is a function of regular patterns of behaviour (“regularity all the way down”), and we are unable even to conceive of any kind of objective causal necessity that goes beyond this...