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Can There be Spatially Coincident Entities of the Same Kind

Published online by Cambridge University Press:  01 January 2020

David B. Hershenov
Sate University of New York, Buffalo, NY 14260-4150, USA


The majority of philosophers believe that the existence of spatially coincident entities is not only a coherent idea but that there are millions of such entities. What such philosophers do not countenance are spatially coincident entities of the same kind. We will call this ‘Locke's Thesis’ since the denial goes back to An Essay Concerning Human Understanding. It is there that Locke wrote, ‘For we never finding, nor conceiving it possible that two things of the same kind should exist in the same place at the same time, we rightly conclude that, whatever exists anywhere at any time, excludes all of the same kind, and is there itself alone.’ It is not clear to me that the believer in spatially coincident entities can draw the ‘ontological line’ where Locke does. Many of the reasons that lead Locke and others to maintain that there exist spatially coincident entities of different kinds would also suggest that there are spatially coincident entities of the same kind. To illustrate this claim, a scenario of spatially coincident roads will be presented.

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Copyright © The Authors 2003

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1 For the traditional view, see Locke, John An Essay Concerning Human Understanding, Nidditch, Peter ed. (Oxford: Oxford University Press 1975), 328Google Scholar. Wiggins, David has written the seminal modern essay ‘On Being in the Same Place at the Same Time,’ Philosophical Review 77 (1968) 90–5CrossRefGoogle Scholar. The richest recent defense is by Baker, Lynne Rudder Persons and Bodies: A Constitution View (Cambridge: Cambridge University Press 2000)CrossRefGoogle Scholar. For a fuller list of references, see Eric, Olson The Human Animal: Identity Without Psychology (Oxford: Oxford University Press 1997), 175Google Scholar n. 3. A minority of philosophers do not believe that there exist spatially coincident entities of different types. I place myself in this group. See Inwagen, Peter van Material Beings (Ithaca: Cornell University Press 1997), 97–102;Google Scholar Zimmerman, DeanTheories of Masses and Problems of Constitution,’ Philosophical Review 104 (1995), 90CrossRefGoogle Scholar; Burke, MichaelCopper Statues and Pieces of Copper,’ Analysis 52 (1992) 12–17CrossRefGoogle Scholar; and Carter, W.R.Our Bodies, Our Selves,’ Australasian Journal of Philosophy 65 (1998) 308Google Scholar

2 Oderberg, David suggests that Locke's thesis be described as one forbidding spatially coincident substances of the same kind. This is because there could be two nonsubstances of the same kind in the same place. Two shadows or two waves could occupy the same place but they are not substances. ‘Coincidence Under a Sortal,’ The Philosophical Review 105 (1996) 145–71CrossRefGoogle Scholar. Though I am sympathetic to Oderberg's distinctions, for the purposes of this paper I am going to ignore it. This won't have any affect on the paper's thesis and it allows me not to get into debates about what makes something a substance, whether there are any, how do they avoid reduction to bare substrata, whether we must speak of bundles of tropes, etc.

3 Locke, An Essay Concerning Human Understanding, 328Google Scholar

4 It is assumed throughout this paper that the alleged spatially coincident entities are composed of the same matter.

5 Hughes, ChristopherSame-Kind Coincidence and the Ship of Theseus,’ Mind 106 (1997) 53–67CrossRefGoogle Scholar

6 Gibbard, AllanContingent Identity,’ Journal of Philosophical Logic 4 (1975) 187CrossRefGoogle Scholar

7 An anonymous reviewer brought to my attention that Kit Fine has offered a very different argument against Locke's, thesis in his ‘A Counter-Example to Locke's Thesis,’ Monist 83 (2000) 357–61.Google Scholar

8 Oderberg, ‘Coincidence Under a Sortal,’ 157–9Google Scholar

9 A puddle can't become so small that it survives as a drop, nor can it become so large that it persists as a pond. Nathan Salmon has expressed doubts whether our intuitions really exclude a puddle becoming a pond.

10 Oderberg, ‘Coincidence Under a Sortal,’ 158Google Scholar

11 Oderberg, ‘Coincidence Under a Sortal,’ 161–2Google Scholar

12 This is a modification of Thomson's, Judith car example in her ‘Statue and the Clay,’ Nous 32 (1998) 149–73.CrossRefGoogle Scholar

13 Hughes, ‘Same Kind Coincidence and the Ship of Theseaus,’ 59–60.Google Scholar Hughes mentions that E.J. Lowe advances an account of assumptions similar to the Unger-inspired one that I present later in this paper.

14 Perhaps this belief is false and its attraction the result of merely watching too many science fiction shows in our youth. But even if that is that case, the thought experiment will still help elicit some revealing facts about our attitudes towards part assimilation.

15 My discussion of assimilation is indebted to Peter Unger's, Identity, Consciousness, and Value (Oxford: Oxford University Press 1991), 147–56.Google Scholar

16 Perhaps it will help if the reader imagines a scenario in which he is in the Situation of a twin on an older planet. If an explosion blows his body into millions of microscopic parts and by chance his matter, piece by piece, slowly ends up identically arranged in an already existing twin on a distant planet who finally has the exact same psychology and physiology as the reader did at the time of his death, has the reader been resurrected? On the contrary, it seems more plausible to say his parts have been assimilated into the body of his twin, rather than that he has been restored to life.

17 The result would be different if we imagine that the constitutive matter of Sea-Ship was replaced in its entirety by two large sections of boat from a cut up Land-Ship. This thought experiment may be more effective if the first of the two sections constituted more than half, say three-fourths of Land-Ship, the second section containing the rest. This event of large part replacement doesn't seem much different from Sea-Ship being destroyed and then a qualitatively identical boat made out of numerically distinct matter. In both cases we would most likely assert that a new and distinct boat had taken the place of Sea-Ship. We may have the same reaction if Sea-Ship's matter were replaced in its entirety by small parts in a matter of seconds. But when the exchange of parts is a gradual one involving small pieces, which is more like what happens in the actual repair of boats while at sea, one is most confident that a boat has survived the replacement of its parts.

18 Some readers may share a worry of an anonymous reviewer that something like biological assimilation is needed in boats to show why additional planks will be absorbed into the existing boat rather than lead to the relocation of the boat the additional planks had composed or the creation of a new boat. While a boat is not responsible for replacing its parts as is an organism — the latter, as Aristotle famously observed, having such power within it — the parts of a boat do work together in a manner somewhat analogous to how the parts of an organism work together in order that the whole can perform its function. The ship's crew or others replace worn out parts much as an organism does. Perhaps due to the fact that the cause of this change is external to the boat, or because any more than half of the parts being removed gives rise potentially to another object with that greater than 50% having a claim to be the original boat, readers may not be sure whether a boat can undergo full part replacement. However, there are some commonalities between boats and organisms. The importance of new parts being caught up with old parts in a functioning whole is perhaps the reason for our greater reluctance to admit the boat survives large or quick changes of most of its parts. And the importance of functioning to assimilation may also account for the reluctance some readers may harbor towards allowing a non-functioning boat stored in dry dock or kept in a museum to survive the same degree of changes that a working boat can. To reinforce this line of thought, imagine that a boat on shore is disassembled and the planks stacked in a warehouse. Its stored planks are destroyed one by one and replaced with new planks. Then the planks are reassembled. The reader may be more reluctant to admit it is the same boat in this case than if the same changes occurred in an intact and functioning boat at sea. This may be because the new planks on land didn't contribute to the functioning of a boat, and thus they don't appear to be assimilated. So the original boat, which perhaps could survive in a scattered form when its boards were stacked, cannot survive much part replacement while in scattered form. Thus there is something remotely similar between part assimilation in functioning boats and part assimilation in functioning organisms.

19 An anonymous reviewer brought to my attention the need to make the destroyed section of road out of a material that could be reused when the road was rebuilt; otherwise, the original road would be an artifact that could survive complete part replacement. Since this assumption of total part replacement is controversial, my thesis of spatially coincident entities is better served if it can be avoided.

20 Nathan Salmon brought to my attention this distinction between impassable, nonfunctioning but existing roads and nonexisting roads.

21 Two anonymous reviewers expressed this concern.

22 Oderberg, ‘Coincidence Under a Sortal,’ 162–3Google Scholar

23 Cartwright, Richard is the locus classicus for this type of response. See his ‘Scattered Objects’ in Analysis and Metaphysics, Lehrer, K. ed. (Dordrecht: D. Reidel 1975) 153–71.CrossRefGoogle Scholar

24 Van Inwagen does just this in his Material Beings. I happen to be sympathetic to his extremist ontology. But that is the matter for another essay.

25 An appeal can't be made to usage to determine whether it is an anvil or a barn door jamb that has been made. This is because the entity may sit on a shelf for a year after being made. Surely, its sortal identity cannot be in limbo.

26 Parfit, Derek Reasons and Persons (Oxford: Oxford University Press 1983), 298–9Google Scholar

27 Baker offers a constitution solution to the problem of spatially coincident thinking beings in her Persons and Bodies. Shoemaker offers a different constitution solution to the same problem in his ‘Self, Body and Coincidence,’ Aristotelian Society Supplement (1999) 287-306.

28 Baker thinks the problem of the lump being contingently a statue, or the organism contingently a person is such a pseudo-problem. See her account of constitution in her Persons and Bodies, 170-4.

29 I would like to thank Nathan Salmon, Frances Dauer and especially two anonymous reviewers for very helpful comments.

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