- Roughly speaking, perdurantism1 is the view that ordinary objects persist through time by having temporal parts, whilst endurantism2 is the view that they persist by being wholly present at different times. (Speaking less roughly will be important later.) It is often thought that perdurantists3 have an advantage over endurantists4 when dealing with objects which appear to coincide temporarily: lumps, statues5, cats, tail-complements, bisected brains, repaired ships, and the like. Some cases – personal fission, for example – seem to involve temporary coincidence between objects of the same kind. Other cases – a cat and its flesh, a statue6 and its lump – seem to involve objects of different kinds.
- When two objects temporarily coincide, they are indiscernible in many basic, temporary respects, but they are discernible in respect of their future careers or past histories. How can this be? How can indiscernibility in all sorts of immediate, ordinary respects fail to guarantee indiscernibility in every respect? This is the ‘temporal grounding problem’.
- According to perdurantists7, temporary coincidence is mere sharing of (temporal) parts. Whilst the objects coincide, they share temporal parts, but when they diverge they do not. The spatial analogy is familiar: these chunks of tarmac right here are parts of both High Street and the Great North Road, those chunks of tarmac over there are parts of the Great North Road but not of High Street. Moreover, we do not expect High Street and the Great North Road to be indiscernible merely because they share a few parts: there is no ‘spatial grounding problem’. The partial-overlap account of temporary coincidence is commonly taken to solve the temporal grounding problem, and thereby to secure some advantage for perdurance8 theory over endurance theory.
- This advantage is not conclusive: perdurantism9 and endurantism10 compete on various fronts, and if endurantists11 triumph elsewhere, they may simply accept that some differences between temporary coincidents are ungrounded, or else argue that temporary coincidence never occurs. Moreover, the perdurantist12 story about partial overlap does not apply where objects appear to coincide permanently: here perdurantists13 and endurantists14 have similar resources available. Nevertheless, a straightforward account of temporary coincidence is a valuable prize, not least because it provides the ontological resources for an epistemicist or a semantic-indecision account of vagueness in persistence: such accounts standardly require hordes of almost-indiscriminable temporarily-coincident objects.
- Ryan Wasserman has challenged the idea that perdurantists15 have any advantage in accounting for temporary coincidence (Matthew McGrath makes a similar point, to which I will return below; see also "Lowe (E.J.) - Material Coincidence and the Cinematographic Fallacy: A Response to Olson" (2002)). "Wasserman (Ryan) - The Standard Objection to the Standard Account" (2002) argues that, insofar as perdurantists16 may invoke the fact that temporarily coincident objects differ mereologically at other times, endurantists17 may invoke a similar fact. Temporarily coincident enduring objects differ in their spatial parts at times when they do not coincide; trivially so if one of them goes out of existence. If other-time differences in temporal parts can ground differences between temporarily-coincident perduring objects, then surely other-time differences in spatial parts can do the same job for temporarily-coincident enduring objects. There is, Wasserman suggests, nothing exclusively perdurantist18 about grounding present differences in other-time mereological differences. What makes these coincident objects distinct? Why, the fact that they will have different parts in the future!
- It is of course true that, if two enduring objects coincide temporarily, then they differ in what parts they have at some other time, and that this is a mereological difference between the two. Why then did anyone ever think that endurantists19 had a special difficulty with the temporal grounding problem? And exactly how was the perdurantists’20 invocation of mereological difference between temporary coincidents supposed to solve the problem? To recover the advantage for perdurantists21, we need to examine questions of grounding or determination. If we could describe the world without commitment to facts about persistence or identity, endurantists22 and perdurantists23 would agree on that description: if they disagreed about this, we could hope to rule out one of them empirically. The temporal grounding problem concerns determination or dependence, not just correlation or supervenience24 (so does the analogous modal25 problem, as "Bennett (Karen) - Global Supervenience and Dependence" (2004) and "Shagrir (Oron) - Global Supervenience, Coincident Entities and Anti-Individualism" (2002) have shown); it challenges us to identify a qualitative ground for differences between the temporarily coincident objects in question.
- So if there is a special difficulty for endurantists26 here, it is because endurantists27 have a special reason to think that facts about number, identity or sort must be determined by temporally intrinsic facts, a reason which does not apply to perdurantists28. And indeed a special reason does seem to present itself. An enduring object is wholly present whenever it exists. The notion of ‘being wholly present at’ a region has resisted uncontroversial clarification, but must involve localness somehow: if an object is wholly present at a region, then important facts about it are determined by what’s going on within that region. In contrast, if an object is only partially present at a region, then we do not expect the central facts about it to be exhausted by what’s going on in that region.
- The main goal of this paper is to substantiate the thought that endurantists29 and perdurantists30 should differ about what determines what, that they should disagree about temporal intrinsicness.
- First, I will clarify the temporal grounding problem, distinguishing two versions of it (section 2).
- Then, I will examine the differences between endurantism31 and perdurantism32 (section 3), and
- Show how perdurantism33 is better placed with respect to the temporal grounding problem (sections 4 and 5).
- Finally, and briefly, I will make some connections between the temporal grounding problem and ‘metaontological’ scepticism about the distinction between perdurantism34 and endurantism35 (section 6).
- Two Temporal Grounding Problems
- Temporal Extent and Temporal Parts
- The Region-Focused Temporal Grounding Problem
- Object-Focused Temporal Grounding Problems
- Distinguishing Endurantism36 and Perdurantism37
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