Lynne’s theory of personal identity allows for a person’s surviving death by leaving this body behind and acquiring a new one, without the need for an immaterial soul that inhabits both bodies. The details of her theory are a bit complicated, turning upon some technical philosophical notions: (1) a “first-person perspective”; and, (2) the “exemplification” of a property.
A “first-person perspective” is, Lynne says, a “dispositional property” — an ability to think of oneself in a “first-personal” way; and it is, she thinks, essential to persons. A dispositional property is what philosopher’s call a universal, something that can be exemplified by many different persons. If Lynne is right, the mental ability of being able to think of oneself in this first-personal way is common to all persons, exemplified by all of them, and so “universal” within the group of persons. But, metaphysician that she is, Lynne is prepared to posit more things than just the individual persons and the common property they exemplify; there is also each person’s exemplification of that one property. Exemplifications of a property by a number of persons are rather like events; each exemplification is like an event happening to just one of the persons. For example, all the members of a dance troupe might kick the same type of kick, one after the other. Kicking in that way is a common property, a universal, something that each of them exemplifies. But it is natural to say that, in addition to each dancer and the universal property of kicking in that way, there are the individual kicks that happen one after another — a series of events consisting of each individual’s exemplification of the property. Lynne is supposing that something similar is true even for dispositional properties; when many persons exemplify the same dispositional property, there is a different exemplification of that property for each person — and it is to these exemplifications that she appeals in her theory about personal identity.
So I have a dispositional property, an ability, which she calls a “first-person perspective.” And in addition to me and the property, there is a further event-like thing: my particular exemplification of this property — which is different from your exemplification of it, even if we are exactly similar in our psychological abilities. What is the point of introducing this further thing, this exemplification of the first-personal disposition? Lynne makes use of exemplifications in stating persistence conditions for persons: “the persistence condition for persons over time is sameness of exemplification of first-person perspective.” In other words, for some future creature to be the same person as me is for its exemplification of this disposition to be the same as the one associated with me now. On her view, the matter in my body could cease to exemplify a first-person perspective (say, when this body dies), so that I cease to be constituted by it; and then, elsewhere in time and space, some future creature could be made of entirely different stuff, exemplifying the ability to think of itself in a “first-personal” way; and, so long as that creature’s exemplification of this power or ability is the same as my current exemplification of it, that creature would be me.
What does it mean to say that “sameness of exemplification of first-person perspective” is the criterion of personal identity, and that it is compatible with all-at-once changes of constituting matter? It is comparable to taking some essential power or disposition of a planet — say, the attractive powers it has in virtue of being an essentially massive body — and then saying that the identity of a planet’s exemplification of this power provides its conditions of persistence, and that identity of exemplification is consistent with being made out of completely different matter. The minerals constituting a planet could be blown apart, and somewhere else similar matter could come together to form a planet, and that planet would be the very same planet so long as its exemplification of gravitational attractive power is the very same exemplification as the one associated with the earlier planet. Lynne does not think that exemplification of this particular disposition — gravitational attraction — can be used to give persistence conditions for anything that could jump from one batch of minerals to another in this way. But the proposed theory of planetary identity has the same structure as her theory of personal identity.
Can anything positive be said about the conditions in which an exemplification of a first-person perspective by something at one time is the same as the exemplification of a first-person perspective by something at some other time? Lynne says that “being a person does not consist in satisfying nonpersonal or subpersonal conditions, such as psychological or physical continuity.” In particular, a future person, created by God out of whole cloth, could exemplify my first-person perspective — and so be identical with me — without displaying any psychological or physical continuity with me. The only thing that can be said about sameness of exemplification of first-person perspective is that it is the same if and only if it belongs to the same person. The notion of an exemplification of a property is introduced to provide persistence conditions, but the conditions turn out to be trivial ones. At bottom, sameness of person is a brute fact on her view, one that can float free from facts about what happens to the bodies that constitute persons and the mental states that are associated with these bodies.
For my part, I cannot make much out of such brute facts for complex material objects. If one group of things, like organisms, consists entirely of atoms in various configurations, then the whole history of the universe told in terms of what the atoms do will tell the whole history of what the organisms do. Given that they are made entirely out of atoms, the organisms cannot jump around independently. Fix the locations in space and time of all the atoms, and one has determined all the facts about where the organisms are, and which are identical with which.
Lynne finds the idea of a soul — an immaterial thinking substance — “incomprehensible” (but presumably only in the finite case; she believes in at least one immaterial thinking substance, namely, God). I find incomprehensible the idea that an entirely material object, with the size and shape and constitution of an organism, could be unconstrained in its trajectory by the histories of all the bits of matter in the universe. Her persons are able to pass like shadows over the physical stuff of our world, jumping from one place to another without constraint — without the transfer of any physical stuff, or even the transfer of energy or information. I am prepared to grant that there may be highly derivative entities capable of such feats — things like restaurants, which can “move” from one side of town to the other in virtue of the signing of a contract, without any movement of bricks or wood. But highly derivative things do not have a significant causal impact on the rest of the world — at least, not in their own right. It’s not the restaurant as such that takes up space, reflects light, and so on. A particular assemblage of brick and wood does these things — whichever one happens to constitute the restaurant at a given time. All the mundane powers of the restaurant are, in the first instance, powers exercised by more fundamental physical substances.
So, though I certainly want to allow that there exist things like restaurants, which can jump from one place to another without the transfer of matter or information, changing all their parts at once, I take them to be highly derivative entities: they may coincide with real physical objects, with real physical powers and propensities, but they do not themselves have causal powers in any full-blooded sense.
When some physical stuff comes together to compose an object, the arrangement and nature of the bits of stuff confers upon the object certain powers and propensities, including tendencies to continue to exist under some circumstances and cease to exist under others. Some of the properties of the whole will be predictable in boring ways from those of the parts — for example, the mass of the whole from the mass of the parts, the location of the whole from the location of the parts. Others might be more surprising, perhaps even deserving of the label “emergent” properties. However, I do not see room for two physical objects made out of the same stuff arranged in the same way but differing in their causal powers and propensities, including differences in their ability to continue to exist. So I have problems with Lynne’s coincident physical objects — objects that are exactly similar in their constitution, but they differ markedly in some of their powers. The organism that coincides with me is exactly like me, but it cannot survive squashing, while I can — by “jumping into” some other organism elsewhere.
There is an example of something like complete coincidence at a time that I can make sense of, but it involves entities of very different kinds. In formal logic, mathematics, and allied subjects, it is important to have a clear notion of a set, class, or collection of things. A set of things is not a whole with those things as its parts; it is those things “taken as many,” and it will exist even if they do not compose a whole (assuming not every group of things automatically composes something larger). The notion of a set of things implies the existence of a special kind of set: namely, the singleton, a set containing just one thing as a member.
Let’s dig further into the relationship between a thing and its singleton. If I can make sense of the notion of a set with just one member, I can make sense of this distinction; and it is an example of something like coincidence of two objects at a time. For example, since I am the only member of my singleton — the set that contains just me — it is not crazy to say that my singleton is located where I am (where else would it be?). It sounds slightly stranger to assign it the same weight as me. It sounds odder still to say that, when I kick something, the set that contains only me kicks it too; but it is hard to say exactly what’s wrong with saying this. Still, the way in which a set can have a location, a mass, and physical effects is entirely derivative — it is the member, in the first instance, that has these properties; the set does nothing by itself.
Sets — and the more elaborate sets known as “functions”, which can be thought of as sets of ordered pairs — can be used to generate all kinds of derivative entities to play the roles of restaurants and other things that borrow their causal powers from more fundamental physical objects. The function that pairs each time with the hunk of wood and brick that makes up a certain restaurant at that time can be simply identified with the restaurant. Then there’s little mystery about how it can be in the same place at the same time as a hunk of wood and brick. After all, the sense in which the function is located in space at a time is rather different, more indirect; it is entirely in virtue of the fact that the hunks of matter paired with the times have location in a more fundamental fashion. There is also no mystery about how the restaurant can jump across town without the movement of any physical stuff. A function “jumps” only in the sense that the function pairs neighboring times with non-overlapping physical objects. Since functions are not physical objects subject to physical laws, no laws are violated by such behavior.
All the best ways to make room for coincident objects — at least all the ones I know of and can understand — are similar to this one; they allow for things that can jump around without transfer of matter or information, but they do so by treating them as derivative entities — more abstract than the hunks of matter that are doing the real pushing and pulling in the physical world. Since I take myself to be a genuine cause, something that does some real pushing and pulling, I can’t bring myself to believe that I am a function or anything like a function. So, I cannot believe that I am a derivative entity, as the only promising form of coincidence would require.