"The Acts of the Apostles provides evidence that Christian proclamation was engaged from the very first with the philosophical currents of the time. In Athens, we read, Saint Paul entered into discussion with 'certain Epicurean and Stoic philosophers' (17:18); and exegetical analysis of his speech at the Areopagus has revealed frequent allusions to popular beliefs deriving for the most part from Stoicism. This is by no means accidental. If pagans were to understand them, the first Christians could not refer only to 'Moses and the prophets' when they spoke. They had to point as well to natural knowledge of God and to the voice of conscience in every human being (cf. Rom 1:19-21; 2:14-15; Acts 14:16-17). Since in pagan religion this natural knowledge had lapsed into idolatry (cf. Rom 1:21-32), the Apostle judged it wiser in his speech to make the link with the thinking of the philosophers, who had always set in opposition to the myths and mystery cults notions more respectful of divine transcendence." -- Pope St. John Paul II, Fides et Ratio

Thursday, October 9, 2025

A Painful Personite Problem for Stage Theory


All the world's a stage, and all the men and women merely players; they have their exits and their entrances, and one man in his time plays many parts.
— William Shakespeare

I. Introduction

Mark Johnston has argued that four-dimensionalist theories of persistence have “surprising, repellent and perhaps even disastrous, implications for our ordinary moral outlook.”[1] In response, Alex Kaiserman has argued that these disastrous implications afflict only one kind of four-dimensionalism, namely, worm theory, but that they do not afflict the alternative stage theory.[2] In this post, I argue that given some plausible premises having to do with pain and moral status, stage theory does not in fact escape the problem raised by Johnston.


II. The Personite Problem and the Stage Theory Solution

The problem raised by Johnston against four-dimensionalism is that it is committed to the existence of personites. Some standard four-dimensionalist terminology is needed in order to precisely define a personite.[3] Take parthood-at-t as an undefined primitive relation that is reflexive and transitive. Two objects overlap at a time iff there is something which is a part of both of them at that time. A thing x is a fusion at t of class S iff (i) every member of S is a part of x at t and (ii) every part of x at t overlaps at t some member of S. Things x and y coincide at t iff they overlap at t exactly the same objects. Lastly, x is an instantaneous temporal part of y at t iff (i) x exists at, but only at, t, (ii) x is part of y at t and (iii) x overlaps at t everything that is part of y at t. From here, four-dimensionalism itself can be defined as follows:

Four-Dimensionalism: Every object has an instantaneous temporal part at every time at which it exists.

Now, let us say that something is a person-stage iff it is an instantaneous temporal part of a person. Let R be the relation between person-stages that secures personal identity through time.[4] Then we can define worm theory and stage theory (with respect to persons) as follows:

Worm Theory: Persons are maximal R-interrelated fusions of person-stages.

Stage Theory: Persons are person-stages.

We can now define a personite as follows:

Personite: If x is a person, then y is a personite of x iff y is a temporally continuous non-maximal R-interrelated fusion of two or more person-stages, each of which is R-related to every instantaneous temporal part of x.

Now, the personite problem can be characterized as follows. Given that I am a person, there are a very large number of personites associated with me. There is a personite that existed over the first ten years of my life and then ceased to exist, another personite that has existed over the last ten minutes of my life and still exists, a personite that will exist in an hour and go out of existence thirty seconds later, and so on. If these personites have moral status, then things like prudential self-sacrifice, making onerous promises for the good of others, and punishing criminals become (deeply) morally wrong.[5] For instance, deciding to undergo substantial short-term sacrifices in order to gain a great long-term benefit for yourself is wrong as it subjects all of the many personites that exists over and only over the interval of sacrifices to great hardship without any benefit. Indeed, hardship is all that such personites will ever go through! Johnston’s argument that personites have moral status can be formulated as follows[6]:

  1. For all possible worlds w and possible objects x, if x is a person in w then x has moral status in w.
  2. For all possible worlds w and v and possible objects x and y, if x in w is a duplicate[7] of y in v, then x has moral status in w iff y has moral status in v.
  3. For all personites x, there are a possible object y and a possible world w such that y is a person in w and y in w is a duplicate of x in the actual world.
  4. Therefore, all personites have moral status.

In response to this argument, Kaiserman grants (1) and (2) but argues that if stage theory (as opposed to worm theory) is true, then (3) is false. For according to stage theory, a person is a person-stage, not a fusion of (two or more) person-stages. Thus, there is no possible person that is a duplicate of an actual personite.[8] Thus, (3) is false, and the inference to (4) is thereby blocked. The stage theorist has eluded the personite problem.

I now turn to a critical evaluation of Kaiserman’s stage-theoretic response to the personite problem.


III. Critique of the Stage Theory Solution: The Problem of Pain

What I want to argue is that stage theory has a problem with accounting for pain, and the most plausible solution to this problem exposes stage theory to the personite problem. The upshot is that even if Kaiserman has escaped from one particular argument for the personite problem, he has not escaped the problem itself. The main idea is this: Pain takes time. More precisely, for humans at least, there is a minimum duration of time such that if a pain is shorter than this duration, then a human cannot experience it.[9] One way to understand this is that a human experience of pain is temporally extended. Now, here is a plausible thesis: a temporally extended experience can only be had by a temporally extended experiencer. It follows that if humans experience pain, then humans are temporally extended.

This is where stage theory runs into a problem. For according to stage theory, persons are person-stages, and person-stages are instantaneous (i.e., temporally unextended) entities. It follows that persons—human ones at least—cannot experience pain. But humans clearly do experience pain! If this is so, then humans cannot be person-stages. Given a four-dimensionalist, stage-theoretic ontology, what, then, could humans be? I submit that the most plausible answer is that humans are fusions of human person-stages such that the fusion is sufficiently temporally extended to be able to have a human experience of pain. The upshot of this is that humans are then by definition personites.[10]

Now, here is another fact about humans: they undergo physical suffering. Plausibly, physical suffering entails pain (though the reverse is likely not true). If this is right, then physical suffering requires temporal extension as well so that person-stages cannot physically suffer. So, given that humans are (most plausibly understood as) personites and given that humans suffer, it follows that personites (human ones at least) suffer. From here, we can observe a plausible principle of moral status: Anything that can suffer has moral status.[11] The conclusion is that (human) personites have moral status. The personite problem has returned to the stage.

What might the stage theorist—Kaiserman in particular—say in response to this argument? Consider the following two objections:

Objection 1: Although each person-stage lacks temporal extension, the same person persists across the person-stages, across an extended temporal interval. Thus, it would seem that a (human) person can experience pain even assuming that temporal extension is required in order to do so.

Objection 2: Even if the argument for personites having moral status on stage theory is sound, it does not follow that personites have full and equal moral status, and this was Johnston’s contention.[12]

In response to the first objection, I would argue that while persons ‘persist’ according to stage theory, they do not really persist.[13] What I mean is that while stage theory provides truth conditions for our ordinary language statements about the persistence of persons, these truth conditions do not consist in persons really persisting any more than the mereological nihilist’s truth conditions for ordinary language statements about ‘composite objects’ consists in there really existing composite objects. On stage theory, each person (which just is a person-stage) of necessity exists only for an instant.[14] To say that a person persists from a time t1 to a later time t2 is to say that there exists a person-stage (person) S1 at t1 and a numerically distinct person-stage (person) S2 at t2, and S1 and S2 stand in an appropriate counterpart relation. So, no person really exists in a temporally extended way. Perhaps the stage theorist can say that while no individual person-stage experiences pain, a number of them collectively experience pain. But this collectivity sounds suspiciously like a fusion of two or more person-stages, which just is a personite. Thus, in my view, the objection does not succeed.

Finally, in response to the second objection, I am inclined to concede the point that my argument does necessarily not show that personites have full and equal moral status. I think it is plausible, for instance, that some non-human animals can suffer and yet have lesser moral status than we do. Nevertheless, given the sheer number of personites (and consequently the sheer quantity of potential suffering) involved, I think that there is still a significant personite problem that remains for the stage theorist. So, while I am willing to concede that Kaiserman has potentially lessened the personite problem for stage theory, I nevertheless maintain that he has in any case not eliminated it. Even if he has lessened it, however, the extent to which he has lessened it bears further investigation.

Moreover, as Alex Pruss has pointed out to me, what goes for pain plausibly goes for all conscious states so that (human) consciousness in general requires temporal extension. If this is right, then on stage theory, human persons turn out not to be conscious while (human) personites turn out to be conscious. Consequently, it would seem that human personites actually have more moral status than human persons, and this makes the personite problem even worse for stage theory than it is for worm theory. Further, it is plausible to think that whatever cannot be conscious isn't even a person in the first place so that person-stages cannot be human persons. If this is correct, then stage theory fails on grounds wholly independent of the personite problem. I conclude that stage theory is simply inadequate as a theory of persons.

 

References

Johnston, M. (2016). Personites, Maximality and Ontological Trash. Philosophical Perspectives30(1), 198–228. https://doi.org/10.1111/phpe.12085

Kaiserman, A. (2019). Stage theory and the personite problem. Analysis, 79(2), 215–222. https://doi.org/10.1093/analys/any074

Koons, R. C., & Pickavance, T. H. (2017). The Atlas of Reality: A Comprehensive Guide to Metaphysics. Wiley Blackwell.

Parfit, D. (2012). We Are Not Human Beings. Philosophy, 87(1), 5–28. https://doi.org/10.1017/s0031819111000520

Pruss, A. R. (2025, August 8). Consciousness and the open future. Alexander Pruss’s Blog. https://alexanderpruss.blogspot.com/2025/08/consciosuness-and-open-future.html

Sider, T. (1997). Four Dimensionalism. Philosophical Review, 106(2), 197–231. https://doi.org/10.2307/2998357

 

 



[1] Johnston (2016), pp. 199.

[2] Kaiserman (2019).

[3] This terminology is provided by Kaiserman (see pp. 215-216). Similar definitions can be found in Sider (1997).

[4] Kaiserman lists psychological continuity and bodily continuity as possible candidates for R.

[5] For detailed discussion of these issues, see Johnston (2016), pp. 207-210.

[6] This formulation is taken from Kaiserman (2019), pp. 217. For Johnston’s original formulation, see Johnston (2016), pp. 203-204.

[7] Following Kaiserman (2019), say that for all possible objects x and y and possible worlds w and v, x in w is a duplicate of y in v iff x instantiates exactly the same intrinsic properties in w as y does in v (pp. 217).

[8] Cf. ibid., pp. 218.

[9] This idea comes from Pruss (2025).

[10] On this view, one might then say that human persons (person-stages, according to stage theory) are proper parts of human beings (personites, according to my argument). For discussion of the view that human persons are proper parts of human beings, see, e.g., Parfit (2012), pp. 14.

[11] As Johnston (2016) notes, Peter Singer, among others, defends this thesis (pp. 203).

[12] Ibid., pp. 210.

[13] This point about the stage-theoretic account of persistence is also made by Koons & Pickavance (2017), pg. 571.

[14] Ibid.

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A Painful Personite Problem for Stage Theory

All the world's a stage, and all the men and women merely players; they have their exits and their entrances, and one man in his time pl...