Parfit and the Animal Question

Problems of Personal Identity in Animal Liberation Theory

Part I: Parfit and Psychological Continuity

Is there any David Bowie on Mars?

“A machine [teletransporter] puts you to sleep, then destroys you, breaking you down into atoms, copying the information and relaying it to Mars where another machine re-creates you (from local stores of carbon, hydrogen, and so on), each atom in exactly the same relative position as before …”

Is this teletransporter really a means of transport, or rather a mode of death?

In this scenario, is the person destroyed on Earth the same person later re-created on Mars — is this ‘you’ the same ‘you?’ Derek Parfit doesn’t think so but nor does he believe that these two persons are all that different. He does, however, believe that the scenario just described contains all the right ingredients for what matters for personal identity. So, what does matter?

Derek Parfit is a contemporary ethicist and philosopher of mind, whose 1984 work, ‘Reasons and Persons,’ was one of the first publications in modern philosophy to ‘explore the relation between identity and ethics explicitly.’

He is a ‘reductionist’ about the self—in contrast with other philosophers of mind, prominently, Thomas Nagel and Bernard Williams — according to which, facts about persons and personal identity ‘consist in more particular facts about brains, bodies, and series of interrelated mental and physical events.’ For Parfit, the self is grounded in, or anchored to, certain biological, chemical, and neural states in the brain. He holds that the exact replication of these states would give rise to the same mind, and in turn that ‘same’ self.

You can access a biography of Parfit and his work here at

The Teletransporter

Certainly when waking up on Mars, you would feel like you, remember entering the teletransporter … you would even feel the cut on your upper lip from shaving this morning.

Someone wakes up on Mars believing that he is you. Indeed he feels like you, so much so that he can still discern the peculiar throb of that cut on his upper lip — a cut you caught shaving earlier that morning. He can remember entering the teletransporter and even recall being put to sleep. Everything he feels now is you — as you would have been—, certainly as you were then.

“But this can’t be me? Something has changed, something important surely?”

Recall: “A machine [teletransporter] has put you to sleep, destroying you, and them breaking you down into atoms, copying the information and relaying it to Mars where another machine has re-created you (from local stores of carbon, hydrogen, and so on), each atom in exactly the same relative position as before”

The processes we are describing seem very much like those we associate with dying. But is teletransportation as-bad, or even nearly-as-bad, as death?

Parfit thinks probably not. I happen to agree, and I suspect that you do too.

The Branch-Line Case

How, if at all, are you different from your replica(s)?

In another scenario, the Branch-Line Case, we are asked to imagine that the teletransporter on Earth has been modified. Instead of destroying you, this machine can now make an infinite number of replicas of you, copying, blueprinting, and relaying the atomic information.

The machine is faulty, however. Although it copies and blueprints all of your atomic information, beaming it to Mars, and then creating your replica from the same local stores of carbon and hydrogen, and so on — just as before — it does so damaging your cardiovascular system. You have days to live. How should you feel? Should you worry about your ‘death’ on the Branch-Line?

If you are distinct from your replica as the separateness-claim maintains, your imminent ‘death’ on the Branch-Line is probably at least nearly-as-bad, if not as-bad, as ordinary death. But this cannot be true. Your replica on Mars shares all of the same information with you: biological, chemical, neural, and so on, and he remembers everything that you do right up until the moment of your replication. He has the same desires and interests as you do, and he is even prone to the same pangs of joy and guilt as you are. In addition, he will want to act on or against these desires and interests just as you would want to do so: your ambitions for your future are, importantly, his ambitions for his future. He may even spare you painful farewells with your loved ones, since he can return home at any point in the near future to visit with your family and friends. He will speak as you do, and tell the same jokes as you do. He will look, sound, and, crucially, behave, just as you do.

On What (Really) Matters

He will seem to be you, and so ‘death’ on the Branch-Line is certainly not nearly-as-bad or even as-bad as ordinary death. What it feels like to be you, your subjectivity, will of course no longer be an experience you alone possess. And yet, all things considered, it could be much worse— so much so that Parfit believes that death on the Branch-Line is almost-as-good as living; it is probably the next best thing, given all other available options. Why does he think this? Because what matters for survival in these two scenarios is not any particular identity relation—a relation thought to obtain between you now and you then, the same body, or memory as John Locke contended— but, instead, the degree to which you remain psychologically continuous.
We may formulate this as The Psychological Criterion of Personal Identity:

X is the same ‘person’ at time t1 as Y at time t2 if and only if X at t1 is uniquely psychologically continuous with Y at t2.

It just so happens that our psychological continuity more often than not consists in the doings of our “memories, intentions, beliefs/goals/desires, and similarity of character” — the more or less regular succession of which creating strong or weak overlapping chains of psychological connectedness. So it seems that we are often correct to associate the self with a particular identity relation. But this is only accidentally true. What matters, here, not just for survival but for personal identity is not your body, or even your memory, but whether you are psychologically continuous with your replica.

Recall our question, “In this scenario, is the person destroyed on Earth the same person later re-created on Mars”— is this ‘you’ the same ‘you?’” Recall also how I remarked upon Parfit’s answering in both the affirmative and the negative; he denied that they were the same person but denied that their differences mattered. I claimed that he answers affirmatively because what matters for personal identity in these two scenarios had been preserved. In our first scenario, the person later recreated on Mars was psychologically continuous with the person destroyed on Earth, sharing strong, overlapping chains of psychological connectedness in shared memories, intentions, beliefs/goals/desires, and so on. This was true in our second scenario too.

In this scenario, the Branch-Line Case, X (you) at t1 was the same ‘person’ as Y (your replica) at t2 iff* X at t1 was psychologically continuous with Y at t2. And indeed we had no reason to suspect that this should not obtain on the Branch-Line: both persons shared strong, overlapping chains of psychological connectedness in shared memories, intentions, beliefs/goals/desires, and so on. However, recalling also that this new machine might generate an infinite number of these replicas, the case for (your) psychological continuity on the Branch-Line is muddied when we introduce two, three, or four replicas. In this scenario, we imagine instead that your original replica has twice since been replicated, with each of his replicas replicated twice in turn, and so on.

*this is a philosophical shorthand for the logical expression, if and only if.

Provided sufficient, discrete temporal intervals separating each replication, it is quite plausible on this Branch-Line that X (you) at t1 will share few if any strong chains of psychological connectedness with n at t’n, despite sharing many strong, overlapping chains of psychological connectedness with Y at t2, and even Z at t3, and so on. While it will follow from this that each resultant person — replica — on the Branch-Line may be joined by a regular succession of strongly connected, and so psychologically continuous, chains, this will be insufficient to establish (full) psychological continuity from X at t1 to n at t’n.

Further, although we will remark that X at t1 is not uniquely psychologically continuous with n at t’n, it will not follow from this that we could indicate any particular point on that line where the psychological life of X ends and the life of n begins. It is in this respect, then, that I claimed that Parfit seems also to answer our initial question negatively, “In this scenario, is the person destroyed on Earth the same person later re-created on Mars’ — is this ‘you’ the same ‘you?’” It is clear to him that our continuing to talk about persons in terms of identity relations is at odds with our thinking in these scenarios.

We should imagine the person destroyed on Earth and the person recreated on Mars not as the same person, but as uniquely psychologically continuous.

“Very well, but what does this have to do with anything?” Well, quite a lot. Parfit believes that the implications of this Branch-Line Case reveal a great deal more about our own lives’ trajectories, quite apart from our replicas.’ Indeed we will see why when we imagine our own lives as Branch-Lines. If I am to draw my own life across sixty years I will comment that its antipodes exhibit stark differences: even now, aged twenty, I can observe that I recall very few of my earliest memories, intentions, beliefs/goals/desires, and so on. And I suspect this will be true as I progress through life, as I age, and my memory fades, and my intentions, beliefs, goals, desires, and so on, change.

Of course I cannot plot at what point my psychological life, aged twenty, will end, and his psychological life, aged sixty, will begin because at each moment something — some memory perhaps — will link me with my past. But looking backwards, I will clearly discern between the various different stages in my own life. For this reason, Parfit holds that we should instead imagine ourselves not as determinate individuals but as societies, or nations, indeterminate: each part of us linked with another, more or less strongly via our shared memories, intentions, beliefs/goals/desires, and so on. And, just as in societies or nations although I may know you, and you may know him, and he may know her, it is more than possible that she may not know me.

For Parfit we are “bundles of experiences and the question “In this scenario, is the person destroyed on Earth the same person later re-created on Mars — is this ‘you’ the same ‘you?’” is on this view an empty-question. What matters for personal identity is not any particular identity relation, the same body or memory, as we have learnt, but mine and your psychological continuity. Still, how does this relate to the Animal Question — the subject of this series? It is my belief that these thought experiments have practical implications for our understanding of the self that extend across human-nonhuman relations.

But what are these implications according to Parfit? How are they relevant?

(1) Duties to Future Selves: if many selves pertain to one body over its lifetime, are we justified in taking preemptive action to prevent future harm?

  • How may we now be able to talk more convincingly about harms to self? e.g., does employment in factory farming undertaking traumatic work compel future selves to be the recipients of past psychological harms?

(2) The Repugnant Conclusion: “the point up to which a population ought to be encouraged to increase is not that at which the average happiness is the greatest possible but that at which the happiness reaches its maximum.”

If we are just ‘bundles of experiences,’ individual happiness cannot be what really matters. Should we rather take the “point of view of the universe?”

  • Should EAs* redirect their resources from anthropocentric charity to nonhuman animal advocacy in view of the billions more future animal selves who will suffer as a result of anthropogenic climate change and as global demand for red meat, pork, and poultry rises — even if this means that a smaller human population will suffer disproportionately so now?


If you are a vegetarian and you eat eggs, should you, perversely:

  • Purchase foods containing eggs produced in battery farms where the total ‘hen-suffering’ is low but the intensity of ‘suffering-per-hen’ is high?

or, (perhaps) more intuitively;

  • Purchase foods containing eggs produced in free range farms where the total ‘hen-suffering’ is high but the intensity of ‘suffering-per-hen’ is low?

What matters here: (1) total suffering, or (2) individual suffering? Further, what are the consequences of an impersonal ethic for our moral intuitions?

(3) The Rejection of Physicalism: if the same body is neither a necessary nor sufficient condition for the continuation of the self as the Branch-Line Case demonstrated how should we think about the legal concept of persons?

  • We have already ‘determined’ that certain corporations may be regarded as legal persons, and recent court rulings in India have granted this same right to certain cetacean species. But what about persons across species?
    e.g., could we imagine the relation of a blind man to his deaf companion animal as a legally binding relation of trans-species interdependence?


  • What are the implications of this rejection of physicalism for the more recent work of Andy Clark and David Chalmers in the Extended Mind?

How should we respond? I will answer in turn in the forthcoming months.

*Effective Altruists or Effective Altruism.

End of Part I

This series is dedicated to Hilary Putnam (1926–2016).