Weak and Global Supervenience: Functional Bark and Metaphysical Bite?

Weak and global supervenience are equivalent to strong supervenience for intrinsic properties. Moreover, weak and global supervenience relations are always mere parts of a more general underlying strong supervenience relation. Most appeals to global supervenience, though, involve spatio-temporally relational properties; but here too, global and strong supervenience are equivalent. Functionally we can characterize merely weak and global supervenience as follows: for A to supervene on B requires that at all worlds an individual’s A properties be a function of its B properties, where this function varies from world to world. But what are the metaphysical commitments of such a relation? We can make metaphysical sense of this functional requirement only if the properties in question are second-order properties, the functionalist theory of the mind being a conspicuous example. Weak and Global Supervenience Back in the days of free love, supervenience relations were welcomed as harbingers of peace and joy. “Let one hundred supervenience concepts bloom!” came the prophet’s cry.1 And bloom they did! As a result, supervenience now comes in a plethora of permutations: weak and strong, local and global, multipleand single-domain, indiscernible and similarity-based, modal and de facto, all appealing to a variety of ‘possible’s from the familiar metaphysical, nomological, and epistemic to the rarer historical and temporal — a flavor to fit every palate! But, alas, the heyday of supervenience has come and gone. Now, surveying this surfeit of superveniences, we wonder if the multitude of proposed variations are truly useful or rather, in Lewis’s words, “an unlovely proliferation of non-equivalent definitions”?2 Are they aiding us in our quest to unravel the metaphysical mysteries of how one sort of thing can depend upon another? Or do they only help “to add mystery to mystery, to cover one obscurantist move with another,” as Schiffer insists?3 Kim sees the growing numbers of supervenience concepts in the literature as good evidence that they are useful in philosophy.4 Cynics might instead think this merely reflects the ease with which one can alter the standard formulations and thereby create yet another supervenience relation — or, worse yet, another family of them. A thorough house-cleaning would require a careful examination of every supervenience notion that has been proposed, a cure worse than the disease. Rather, I propose to examine the predominant notions of supervenience. Strong supervenience, like all supervenience relations, can be reformulated, more perspicuously I suggest, in 1Kim, “Supervenience as a Philosophical Concept,” p. 155. 2Lewis, “On the Plurality of Worlds,” p. 14. 3Remnants of Meaning, p. 153-154. 4“Supervenience as a Philosophical Concept,” p. 133.