Suppose a man has a cloning machine. It has two chambers A and B. Any person who wants to make a clone of himself/herself enters in chamber A. Then, the machine does one of these two things:

  1. Teleport the original person to chamber B and make their clone in chamber A.
  2. Make a clone of the person in chamber B and the original person remains in chamber A.

But no one knows what the machine does out of these two choices.

Suppose the man uses the machine. After the machine is done cloning, the only difference between the man and his clone is that the man existed before that moment and the clone didn't. But both of them remember using the machine. The clone actually never used the machine but he too has the same memories of using it.

Before the man used the machine, he is sure that he is the original and the other person who is about to be created would be the duplicate. After he is done using the machine, he again is sure that he is the original because he has the memories of using the machine and creating his clone. But if he gives it a little more thought he'd know that, for all he knows, he could be the clone and still be thinking that he is the original.

So, after someone makes a clone of themselves, would they really get confused whether they existed before that moment?

  • 4
    There’s an implicit assumption in your setup that (a) there’s only one person before the procedure and (b) that exactly one of post-procedure people is identical with that pre-procedure person. Yet that’s not obvious: Lewis argued that if both A and B are psychologically continuous with O, then we had two objects in O all along, but they overlapped. (See his ‘Survival and Identity’). On a competing view, O instead dies the moment A and B come into existence. – Before your question can be answered, we must probably first settle personal-identity disputes like this.
    – MarkOxford
    Nov 2, 2017 at 9:53
  • PS: You may also want to look at the Sleeping Beauty Problem, and the debate between Externalists and Internalists in Epistemology.
    – MarkOxford
    Nov 2, 2017 at 10:19
  • 2
  • Suppose I tell you that you've just been cloned and came into existence five seconds ago. How would you disprove that? How do you know you didn't just come into existence with your memories? Maybe you're a Boltzmann brain. Maybe you're a brain in a vat, a program in a cosmic computer. Maybe, as Descartes wondered in 1641, everything you perceive and experience is an illusion created by an evil demon.
    – user4894
    Mar 2, 2018 at 19:48
  • This question has fancy bells and whistles what with the cloning and teleportation and all, but the question really just boils down to this: A man flips a coin but doesn't look at it. Does he have evidence to suggest it came up heads? No - he cannot make any inference about the coin flip. Only the coin flip is a randomly-operating cloner-teleporter and coming up heads is being a clone. May 31, 2018 at 16:01

5 Answers 5


Yes. Though I'd phrase it a little differently: I wouldn't use the word "confused" as much as simply say neither man could know whether his body was just created or not.

Assuming a sub-atomically identical clone, the only way this wouldn't be true is if there is something non-physical that identifies each person as that particular person and that each person is aware of it. Of course, this is the concept of the soul. So, if you are allowing souls, perhaps the person wouldn't be unsure if he were the original or the clone.


We wouldn't know as actual cloning is not possible.

There are two analogues to think about here. The first is genetic twins. they are genetically twins of each other but there is little evidence to think that they seriously disturb a persons sense of reality. They might be a little unsettling to someone whose never met twins before but generally people quickly adapt.

The second analogy is with online virtual avatars where cloning of avatars is quite easily done. This is quite well attested to and can be used to unsettle and disturb a persons sense of reality. This is usually known as gaslighting and can be done by individuals - known as trolls; and where they are organised, as troll farms and troll gangs; and by corporations, where there is no term that I know that is available - perhaps corporate trolling?

  • I don't think we need to be able to do this in order to think about it. I'm not at all sure an actual experiment would clear up the identity issues. Aug 29, 2018 at 22:16
  • @David Thornley: It makes sense to me. It's basically the experimental method. Or the empirical method. I don't see how you can deal with the identity issues of basically the plot of science fantasy fiction. Aug 29, 2018 at 22:51
  • @David Thornley: You can deal with it in terms of the world built up by that piece of fiction but this bears only the most superficial relationship with the real world; and the relationship is backwards - it's the real world that informs and constructs the fictional world and not vice-versa. Aug 29, 2018 at 22:56

On the basis that teleportation isn't noticeably less philosophically confusing than identical cloning, I would conjecture that whoever ends up in chamber B could safely assume that they didn't exist in any meaningful way prior to the transformation.

As the premise of the question is that the person in chamber A can't know whether they are a clone or not, then it is entirely reasonable that they would be confused.

I also note MarkOxford's comment about the Lewis conjectures. If the question had been whether or not they actually did exist prior to the operation then settling those questions would be necessary.

Only if the person was completely convinced that, regardless of what happened, they definitely existed (or not) prior to the operation would the results be different. And that could, of course, occur whether or not it was actually or philosophically true.

  • I think it matters either way whether Lewis was right. On his view, there’s not much to be confused about as there isn’t really a clone: there are two persons before and after the procedure, except they no longer overlap afterwards. Thus both are right in believing ‘I existed prior to the procedure’. The only thing they could be confused about (wonder about), is whether they still inhabit the same body; but that question can be posed without cloning/fission: Just imagine a machine that can swap your body while you sleep, leaving you with an exact duplicate of what you used to inhabit.
    – MarkOxford
    Nov 2, 2017 at 14:14

'So, after someone makes a clone of themselves, would they really get confused whether they existed before that moment?'

What existed before that moment was a being with a subset of unique properties. That being ceased to exist the moment the cloning operation occurred. There is no identity relationship with the pre-cloning body though there is one regarding indiscernibility with reference to what Derek Parfit called 'Relation R- psychological connectedness (namely, of memory and character) and continuity (overlapping chains of strong connectedness). However this 'Relation R' is not unique and thus can't resolve any confusion.


If the two people were identical at some point in the process, they were both in fact both the same person until they were no longer identical. A = B and B = A.

Now five minutes ago your brain and body were in a totally different state. The molecules have been moving around in your brain and body in space time as you have been reading this. You are probably not identical to any of the other yous that live in the immediate past or future in this part of the universe. The molecular makeup of your body also changes over time. This is the puzzle about personal identity. There seems to an assumption you are making about time in there. It could be that there is nothing changing. The people could be like little similar cartoon figures written on the pages of a book that only appear to be in movement when you quickly flip the pages.

It is true that we may not be able to really know whether the universe exists more than five minutes ago or not. The whole thing could have come into existence five minutes ago as it was five minutes ago, with all the memories of the past implanted. So we can always have that doubt if we choose. Your experience of the world and memories could also be coming from a random arrangement of some weird goop bubbling away in some unimaginable universe and nobody else has actually ever existed but you. The whole thing could blink out of existence any moment. That’s possible too. There are a lot of possibilities like that that are hard to ever rule out. There could be Gods creating universes just to test one person on something. If there is a God with unlimited power then it could be that none of those terrible things actually ever happened in the past and we don’t know if there is a problem with evil. Or aliens could be creating a simulation and you could be an artificial intelligence undergoing some sort of test, or perhaps people from the future with advanced technology playing some kind of immersive game. I’m not sure how you could ever know. Descartes’ demon can take many forms.

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