Consider the following hypothetical scenario:

Suppose a person (Jack) commits a murder and wants to escape punishment. A brilliant but unscrupulous neurosurgeon hears of this and offers to help. They kidnap an innocent man (Mark) and alter his physical appearance so that he looks entirely like the murderer. On top of that, they also alter the arrangement of Mark's brain neurons so that he thinks exactly like the murderer Jack, and has all the memories/recollections of the murderer.

Now, Jack undoubtedly committed a crime, so it is reasonable for him to receive a punishment. But should Mark be punished too? If not, supposing it is unfair to punish Mark, but given that they are virtually indistinguishable from each other, should both of them be exempted from any form of punishment?

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    What is Personal Identity? Maybe also our "personal history"... May 23, 2022 at 7:33
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    An excellent question. This question presents a challenge to materialists who aren't willing to give up morality. Morality really doesn't make sense in a purely material universe. May 23, 2022 at 8:02
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    This question is no challenge to physicalism, whatsoever. 1st, at this point Mark is gone, consider him dead, his personality and likeness erased forever, debating what should happen to him makes no sense. Add this crime to Jack's counts. 2nd, What is left is Jack, who commited a crime and Jack2, who didn't but is just as dangerous as Jack. Both should be put in jail, 1 to protect society, 2 in the hope of rehabilitation, 3 as a deterrent to people who think about using this same trick effectively sending the signal "don't try, you'll go to jail anyway".
    – armand
    May 23, 2022 at 8:19
  • @armand but why should Mark(aka Jack2) be punished? Firstly, whatever happened to him was without his consent; he was unknowingly turned into who he was. Why should he be punished, when at the point the crime was committed, he had no such "evil" intentions at all? Secondly, to lock someone up under the pretext that he may commit a future crime seems a bit superficial and unfair to me.
    – lalala
    May 23, 2022 at 9:22
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    The problem here is, if you were to face a judge in order for him to decide your status, it already means you must have committed some sort of crime in the first place. This is different from the case of locking someone up just because it is suspected that he could commit a crime in the future (he has done nothing wrong up till now, and it is not even guaranteed he will do anything wrong in the future).
    – lalala
    May 23, 2022 at 9:53

2 Answers 2


Punishment, as we see it, is a legal issue, and legality doesn't concern how one thinks and remembers, only what one has done, and the original Jack was the one to commit the crime, not Mark. So Jack should be punished and not Mark.

Ignoring legality however and simply looking at morals, it concerns possibility with reality. Mark now thinks like a killer and it is reasonable to claim his propensity to kill is much greater, however he has yet to do so. Jack on the other hand thinks and remembers identically, but has actually murdered someone. Clearly, as you stated, Jack ought to be punished. But what of Mark and his possibility?

This reminds me of a certain philosophical perspective on personhood and abortion. Essentially it goes that personhood is attained via acquiring a personality, a set of desires and hobbies-unique, personable things specific to you. If you are pro abortion, you value the woman's life more because she is a person with a developed life and personality, whereas the fetus is not a person because it has not been given any experience or life as to develop this. If you are against abortion, then you value the life of the fetus more, because while you recognize the personhood of the woman, you consider the fetus to be equally a person because, if born, it will develop a personality with desires and hobbies. Therefore the fetus's potential personhood is equal to the woman's developed and remaining potential personhood, and to harm the woman then is less severe than to kill the fetus.

Considering that analogy and the case at hand, there is no definitive answer, it's simply where you place your morality- on the actual, or what may be the actual. However, I would argue you ought to place your morality on the actual. The potential actual is an abstraction, a probabilistic reality that is not grounded or certain. There is nothing more real than the actual, so the potential actual must be less real, by definition. This does however assume it is one or the other; there certainly exists the case where you may value one more than the other, but it's not only the actual or only the potential actual. This is the most realistic case really, in such Jack ought to be punished and Mark ought to be as well, but to a lesser degree and possibly a different form (rehabilitation, therapy, surgery to reverse altered neurons, etc).

  • Outstanding. Welcome. I hope you stick around.
    – J D
    May 24, 2022 at 5:31
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    My understanding is, you can only either punish both (because Jack murdered someone), or neither (because Mark didn't), but unless you can tell them apart (which, you can't, as far as I understand the premise of the question), you can't punish just one because you can't know who the right one is.
    – kutschkem
    May 24, 2022 at 7:26
  • @kutschkem I agree, the employment of the punishments, if any, isn't practical. However, I took the question to ask how punishments ought to be dealt out in an ideal sense, rather than if they practically could. May 24, 2022 at 15:23

Suppose we alter the scenario. We have a teleportation device that kills the original and creates an exact copy at the destination. We would certainly agree that it is reasonable to punish a murderer even after he used that teleportation device.

Now the device malfunctions and creates two copies. Both have, in the past, when they were still one person, committed a murder and should be punished.

Now we put two people in the device, but again it malfunctions and out come two murderers instead of a murderer and an innocent person. Sad accident, but again we punish both copies of the murderer.

Your scenario is similar to that last teleporter accident. Not even Jack and Mark can really tell who is the real Jack, so in some sense, they both are. Mark was killed, and out came a copy of a murderer.

I think this is a reasonable ethical judgement, but a world where this is possible would probably need different laws from ours to make it possible. There is a very real possibility that with our laws, none of the two would be punished to avoid punishing an "innocent".

  • I would not agree that with your first claim that you think we would all agree to. It is not reasonable to punish the innocent clone created by the device because the original committed a crime. The murderer has already been killed by the device and so is beyond justice. How does a materialist defend punishing someone based on his fake memories? What moral principle is served? What materialist principle is being used to justify holding two different material beings as one based on something as non-material as memories? You have a lot more to explain in this answer. May 23, 2022 at 15:22
  • @DavidGudeman I would say to a materialist, if two persons are indistinguishible, they are the same person. There is no material difference between the "clone" and the original, so in that sense, the clone is not a new person without a past, it just shares the past with the original. I would even go so far to say it is simply (to a materialist) the same person. The judgement shouldn't depend on whether the teleporter actually transports or clones, because the end result is the same: a person goes in the one end, and a person that is the same as the one who went in, comes out the other end.
    – kutschkem
    May 24, 2022 at 6:51
  • Would you say that about two rocks? If two rocks are indistinguishable, they are the same rock? Two objects are always distinguishable because they are in different places. May 24, 2022 at 8:05

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