Opening & Closing Paragraphs
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- To persist is to exist at more than one time, to transcend the momentary. How do things achieve this? We might answer with talk of thermodynamic stability, molecular bonds, photosynthesis, the porcupine’s spines, German manufacturing standards, legal protection of ancient monuments, or the uncanny ability of children to extract care from their parents. In Lewis’s terms, such answers explain the existence of spatiotemporal and qualitative continuities over time in causal terms, by reference either to the causal mechanisms which directly underpin such continuities, or to their preconditions and external circumstances. Explanations may differ according to the kind of object in question: German washing machines and yew-trees are both long-lasting, relative to other types of appliance or tree respectively, but the reasons for their longevity are quite different.
- The metaphysicians have a further question about persistence, a question which is expected to have the same answer for all sorts of concrete objects. What is it for something to exist at more than one time? For Lewis, a thing exists at more than one time by having distinct stages, each of which is located at a different time. These stages are parts of the persisting object: added together, they are the persisting object. On this view, persistence through time is analogous to extension through space: a spatially-extended object occupies more than one point at a single time by having different spatial parts located at different places. Likewise, for Lewis, a temporally extended object occupies more than one time by having different temporal parts located at different times. “Persisting particulars consist of temporal parts, united by various kinds of continuity.”
- The intended contrast is the view that concrete things “endure identically through time”, as universals1 do if they exist. Universals2 are wholly located where their instances are: the universal having mass 1kg is entirely present in each of the 1kg bags of flour on the supermarket shelf, and that very same universal will be present in future bags of flour, just as it was in past bags of flour. The universal does not portion itself out, a part here and now, a part there and then: instead, the whole universal is in each place it is needed. In the same way, an enduring concrete thing, if such there be, would not portion itself out over time, a stage then and a stage now: instead, the whole persisting object is located at each time of its existence.
- Following Lewis (who credits Mark Johnston), these rival views of persistence are now known as ‘perdurance theory’ and ‘endurance theory’ respectively:
Let us say that something persists iff, somehow or other, it exists at various times; this is the neutral word. Something perdures iff it persists by having different temporal parts, or stages, at different times, though no one part of it is wholly present at more than one time; whereas it endures iff it persists by being wholly present at more than one time. Perdurance corresponds to the way a road persists through space; part of it is here and part of it is there, and no part of it is wholly present at two different places. Endurance corresponds to the way a universal3, if there are such things, would be wholly present wherever and whenever it is instantiated. ("Lewis (David) - On the Plurality of Worlds", p. 202).
(Lewis had previously used ‘endure’ as the neutral word ("Lewis (David) - The Paradoxes of Time Travel", p.68 in "Lewis (David) - Philosophical Papers Volume II")).
- Lewis touched upon issues of persistence throughout his publishing career, from "Lewis (David) - Counterparts of Persons and Their Bodies" in 1971, to "Lewis (David) - How Many Lives Has Schrodinger's Cat?" in 2004. The most extensive discussions can be found in "Lewis (David) - The Paradoxes of Time Travel", "Lewis (David) - Survival and Identity" and its later postscripts, "Lewis (David) - On the Plurality of Worlds", "Lewis (David) - Rearrangement of Particles: Reply to Lowe", and "Lewis (David) - Tensing the Copula"; he remained committed to perdurance theory at every stage. In this chapter4, I will explore the connections between Lewis’s perdurance theory and his Humean Supervenience5, arguing that his influential argument about temporary intrinsics6 is best seen in this light. I then turn to a domestic dispute within the anti-endurantist7 camp: why does Lewis identify ordinary objects with world-bound parts of transworld objects, but not with time-bound parts of trans-temporal objects? Given that Lewis is a counterpart theorist about modality8, why isn’t he a stage theorist about persistence?
Intervening Sections:- Not all of us share Lewis’s preference for perdurance theory over stage11 theory, and of course not all of us follow him in rejecting endurance theory. But his treatment of this issue – which barely reaches the surface of his writing – is an especially beautiful example of Lewisian metaphysical and semantic views working to support one another. It illustrates the systematicity of his metaphysics, integrating the rejection of worldly indeterminacy and the quasi-identification of parts and wholes with headline issues about worlds, times and properties. And it offers a master-class in the art of recognising both the power and the limitations of analogy.
Footnote 3: Hawley has just spelled out what Lewis means here. But is this completely obvious? I know it’s only an analogy thrown in for illustrative purposes, but is it correct? In what sense are universals “present”, and are they really “wholly present”, even if they are? Take Wittgensteinian “family resemblance concepts” – is the universal “game” wholly present in both rugby and chess? Is the universal “lion” wholly present in each individual lion or is it spread through all past present and future members of the species – which all differ slightly. Might not universals (depending on our theory of them) be just as much of an analogy to perdurantism as to endurantism? Maybe take a look at "Moreland (J.P.) - Universals".
Footnote 4: Of The Blackwell Companion to David Lewis.
Footnote 11: Otherwise known as Exdurance. This is Hawley’s own view.
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