Reconstructing Thought Experiments in Personal Identity

Lasse Nielsen Palacký University, Olomouc, Czech Republic. Reconstructing Thought Experiments in Personal Identity Abstract | Thought experiments are abundant in the topic of personal identity theory as well as in metaphysics in general. While many of them serve to illustrate and guide us through complicated theories and explain difficult to grasp terms, others are irrelevant and muddle the very discussion they aim to clarify. By building upon the work of John D. Norton and Kathleen V. Wilkes, this paper sets out to establish a formula for a good thought experiment. The paper outlines Norton’s theory that all thought experiments can be reconstructed into arguments. His work in this subject refers mainly to thought experiments in science, but the aim of this paper will be to apply his theory of reconstruction to thought experiments in metaphysics. Along with Norton, the work of Kathleen V. Wilkes and her critique of fission thought experiments will likewise be taken into consideration. The paper concludes that for a thought experiment to be successful it must make sense as an argument, after the impossibilities have been eliminated. Keywords | Thought experiments - Personal identity – The Self – The elimination thesis. In a paper from 1991 entitled “Thought Experiments in Einstein´s Work”, John D. Norton first proposed the idea that all thought experiments can be seen as arguments. This idea sprang from the reasoning that as an empiricist philosopher of science, he could not accept that a thought experiment can replace an actual experiment. Norton elaborates on this in his paper from 1996 titled “Are Thought Experiments Just What You Thought?”, arguing that a thought experiment does not involve any new empirical data. A thought experiment can help us see a concept in a new way, but it is all based on past knowledge gained from experience.1 There is no difference then, except for the form, between a thought experiment and an argument. All thought experiments can therefore be reconstructed into arguments. Norton calls this the reconstruction thesis: “All thought experiments can be reconstructed as arguments based on tacit explicit assumptions. Belief in the outcome-conclusion of the thought experiment is justified only insofar as the reconstruction argument can justify the conclusion”.2 According to Norton then, we would be justified in believing a thought experiment if it can justify the conclusion when reconstructed into an argument. Norton states that thought experiments are arguments which: “(i) posit hypothetical or counterfactual states of affair, and (ii) invoke particulars irrelevant to the generality of the conclusion”.3 Point (i) is fairly obvious but (ii) is particularly interesting. Norton claims that there are elements within a thought experiment that have no impact on the conclusion of that argument. John D. Norton, “Are Thought Experiments Just What You Thought?,” Canadian Journal of Philosophy 26, no. 3 (1996): 334. 2 Ibid., 339. 3 Ibid., 336. 1 1 Norton argues that it is possible to remove these from the argument. He calls this claim the “elimination thesis”.4 The elimination thesis in its entirety states: “Thought experiments are arguments which contain particulars irrelevant to the generality of conclusions. Thus, any conclusion reached by a good thought experiment will also be demonstrable by an argument which does not contain these particulars and therefore is not a thought experiment”.5 Transferring this to the field of metaphysics, it could then be argued, that for a thought experiment to be successful it must be able to separate the impossibilities from the conclusion. An unsuccessful thought experiment, in contrast, fails because it bases the conclusion on the counterfactual element itself. In other words, the element that would normally be cut away with the elimination thesis is used as a premise in the argument. This leaves us with an argument that has a conclusion which rests on nonfactual premises. Because of this, the conclusion of the thought experiment cannot be applied to the real world. To illustrate the point, let us look at a very wellknown thought experiment by Derek Parfit. In his book Reasons and Persons from 1984, Parfit constructs a thought experiment in which he enters a teletransporter: “I enter the Teletransporter. I have been to Mars before, but only by the old method, a spaceship journey taking several weeks. This machine will send me at the speed of light. I merely have to press the green button. Like others, I am nervous. Will it work? I remind myself what I have been told to expect. When I press the button, I shall lose consciousness, and then wake up at what seems a moment later. In fact I shall have been unconscious for about an hour. The Scanner here on Earth will destroy my brain and body, while recording the exact states of all of my cells. It will then transmit this information by radio. Travelling at the speed of light, the message will take three minutes to reach the Replicator on Mars. This will then create, out of new matter, a brain and body exactly like mine. It will be in this body that I shall wake up. Though I believe that this is what will happen, I still hesitate. But then I remember seeing my wife grin when, at breakfast today, I revealed my nervousness. As she reminded me, she has been often teletransported, and there is nothing wrong with her. I press the button. As predicted, I lose and seem at once to regain consciousness, but in a different cubicle. Examining my new body, I find no change at all. Even the cut on my upper lip, from this morning's shave, is still there. Several years pass, during which I am often Teletransported. I am now back in the cubicle, ready for another trip to Mars. But this time, when I press the green button, I do not lose consciousness. There is a whirring sound, then silence. I leave the cubicle, and say to the attendant: ‘It's not working. What did I do wrong?’ ‘It´s working’, he replies, handing me a printed card. This reads: ‘The New Scanner records your blueprint without destroying your brain and body. We hope that you will welcome the opportunities which this technical advance offers.’ The attendant tells me that I am one of the first people to use the New Scanner. He adds that, if I stay for an hour, I can use the Intercom to see and talk to myself on Mars. ‘Wait a minute’, I reply, ‘If I´m here I can't also be on Mars’. Someone politely coughs, a white-coated man who asks to speak to me in private. We go to his office, where he tells me to sit down, and pauses. Then he says: ‘I´m afraid that we're having problems with the New Scanner. It records your blueprint just as accurately, as you will see when you talk to yourself on Mars. But it seems to be damaging the cardiac systems which it scans. Judging from the results so far, though you will be quite healthy on Mars, here on Earth you John D. Norton, “Thought Experiments in Einstein´s Work”, in Thought Experiments in Science and Philosophy, ed. Tamara Horowitz and Gerald Massey (Savage, MD: Rowman & Littlefield, 1991), 131. 5 Ibid., 131. 2 4 must expect cardiac failure within the next few days.’ The attendant later calls me to the Intercom. On the screen I see myself just as I do in the mirror every morning. But there are two differences. On the screen I am not left-right reversed. And, while I stand here speechless, I can see and hear myself, in the studio on Mars, starting to speak.”6 Parfit’s point with this thought experiment is to demonstrate that what matters in cases such as these is not identity in a strict one to one relation, but rather survival of personal identity. In the first section of the thought experiment, Parfit sketches out an easy to follow the teletransportation situation, resulting in a non-branching teletransportation. He then describes the same situation with a twist. We are now asked to imagine the machine malfunctioning, leaving us with a copy and the original existing at the same time (a branching form of identity). We have already accepted, according to Parfit, that teletransportation is survivable in terms of identity. We are left with an intuitive feeling that both these Parfit persons are identical to the one that entered the teletransporter. Parfit therefore concludes that a strict one to one identity is not what matters, since we would intuitively argue that Parfit has survived the teleportransportation, despite now having taken a branching form of identity. Reconstructing the thought experiment we find, hidden within, an argument which runs something like this: Premise 1: Personal identity is a one to one relation. Premise 2: Teletransportation is as good as survival. Premise 3: Teletransportation is not a one to one relation. Conclusion: Survival does not require a one to one relation of personal identity. In order for us to accept the conclusion of Parfit’s argument, we would have to accept the second premise, that teletransportation is as good as survival. Yet because this premise is not factual, we should not accept it. An argument based on hypothetical premises cannot yield a non-hypothetical conclusion. We would not be able to apply the elimination thesis to this argument since the impossibilities are what the conclusion rests upon. Parfit argues that we can transfer the intuitive beliefs we have, to cover actual cases.7 It is hard to see how one would go about applying this thought experiment to any genuine situation. We are not presented with this type of teleporter problem in any aspect of real life. We simply do not know how any sort of teleportation can alter our view of identity and merely imagining it will not allow us to gain insight into any element of real life. By creating an obscure sci-fi example, Parfit has muddled the waters of the discussion. The premises are nonfactual, and his thought experiment therefore fails.8 Wilkes speaks of a similar issue with fission thought experiments. 9 For Wilkes, the main problem with thought experiments of this type is that they often suffer from a reality problem. This does not mean that a thought experiment has to be 100 percent realistic. Wilkes argues that although a thought experiment can have some impossible element in it, that impossible element cannot be the one which is the focus of the experiment. When Einstein posed the thought 6 Derek Parfit, Reason and Persons (Oxford: Clarendon Press, 1992), 199-200. Ibid., 200. 8 It is important to note that the scope of this paper is not to debate Parfit’s theory about identity and survival, but to analyses the thought experiment he uses. 9 By fission thought experiment, I here mean all the thought experiments that deal with people splitting or changing body, either through operations, teleportation or unnamed magical processes. 3 7 experiment, where he postulates himself flying next to a beam of light, the impossible act – Einstein flying at the speed of light – in no way changes the properties light has, and the thought experiment was therefore a successful one. When we, on the other hand, introduce person splitting we are changing the very thing we want to investigate because splitting changes the properties of identity.10 Making Einstein’s thought experiment into an argument; it is apparent why Wilkes argues that this thought experiment works. Premise 1: According to Maxwell’s theory of electrodynamics, light, relative to something else at the speed of light, would be rendered as a stationary oscillatory field. Premise 2: A stationary oscillatory field is an impossibility when dealing with light. Conclusion: Maxwell’s theory is mistaken. The element of fiction, Einstein traveling at the speed of light looking at what will occur, can be eliminated from the argument without changing the conclusion; “Thus we need to ensure that what is imagined could be realized in some possible world; or that if it could not be, this impossibility is not ‘relevant’ to the derivation of the conclusion.”11We can apply this to the splitting example above. We see that the premise (when split in two) cannot be eliminated from the argument since it is what the conclusion is based on. Inspired by Norton and Wilkes, a formula can be created for what makes a good thought experiment in personal identity: A thought experiment is valid insofar as it makes sense as an argument, after the impossibilities have been eliminated. The main point with this formula is not only to sort out the logical from the illogical thought experiments, but also to eliminate the irrelevant thought experiments. This means all the experiments that do not allow themselves to be applied to the present way we view a given term. A thought experiment must be able to lend itself to our real world notion of the use of a concept. Another issue that comes up in Wilkes book is the problem of imagination. Wilkes argues that is it not so easy to imagine a possible world where these thought experiments are supposed to take place. To imagine a possible world where people regularly receive a new body would, according to Wilkes, involve too many unknowns for us. How would we know what the result of such a process would be if the background of the possible world where this takes place is not adequately described?12 To explain the point more clearly, we can look at an actual scientific experiment. Here we rightly assume that all the background information is set against our real world, and that all the factors that change are isolated factors which do not influence any other aspect of the world. With a transplant thought experiments, however, there are far too many unknowns. Our ability to imagine the thought experiment is impaired by the lack of detail. We do not know which factors remain the same, and which will be altered based on the setting of the thought experiment. Beck criticizes Wilkes on this point in his paper. He argues that the background of a thought experiment is irrelevant as long as it deals with the concepts we also deal with. He argues that Wilkes misses the mark because what we look for in a thought experiment is our notion of the concept of “person” 10 Kathleen V. Wilkes, Real People: Personal Identity Without Thought Experiments (Oxford: Clarendon Press, 2001), 8- 9. 11 Ibid., 12. 12 Ibid., 9. 4 and how the scenario applies to it: “What we are after is our concept, not the concept that people in the society would use.”13 It seems, however, that Beck has missed a key point of Wilkes argument. Wilkes is arguing that the process of imagining the thought experiment is impossible due to its lack of detail. How does one imagine a world where people split at will? This is not something that is easy to imagine, let alone conclude anything from. It could be argued that the thought experiment, even if it could be imagined, would fail none the less. Becks argument is that we can learn something about our concept of identity and persons by engaging in the thought experiment, but the issue that causes us to reconsider our concept of person and identity, is an issue that only happens in this very special place. It is in all probability true that if one were to find one’s self in such a world, identity and person may have different necessary and sufficient conditions. Living there might force us to reconsider the way we see personal identity. We do not live there, however. We do not engage in people splitting as they do in this possible world. We cannot therefore apply what the people do in their world to the real one. It is difficult to see how this thought experiment can bring us anything of value. It is the same issue we run into when we look at the thought experiment carried out by Parfit mentioned earlier. Beck argues that a thought experiment such as this need only be plausible enough to illustrate the weakness in an opposite theory. It does not play the role of evidence, and it therefore does not need to be as well established as if it were used as actual confirmation. “But performing the task of offering a counter-example – as a refuter – to a claim of necessity has no such onerous requirements. It need only present conditions, as minimal as you like, in which we have a case in which we can apply a concept in the way the theory in question implies we can’t.”14 Many thought experiments are used as counter-examples and some are put to good use. The problem is again the same. The premises must be factual. It is very damaging to a theory like Animalism to have people splitting and functioning normally, but what good is that counter-example if we do not accept the premise that people split? Animalism may suffer in a world where people split, but in this world, the thought experiment does not damage the theory. It is thus an unsuccessful thought experiment because we cannot apply it to the world we live in. To our formula then, we must add the condition that for a thought experiment to succeed, it must be described to a degree that makes it possible for us to imagine the setting. If thought experiments can be reconstructed into arguments, then why do we then use thought experiments instead of arguments? This is a good question. Norton points out that it is easier for us to use a thought experiment than to navigate very complicated arguments.15 We are often dealing with some very theoretical and difficult concepts, and a thought experiment can help us get our thoughts in order. It can thus be an exploitational tool. It can also help set the scene for the argument, making it more convincing by way of explaining some background. We must, however, be careful. If we forget the limitations of the thought experiment, we lead ourselves astray. We end up confusing the issue with fiction rather than fact as Wilkes points out.16 The reconstruction and elimination theses are ways for us to check the validity of our thought experiments. Simon Mark Beck, “Transplant Thought-Experiments: Two Costly Mistakes in Discounting Them,” South African Journal of Philosophy 33, no. 2 (2014): 192. 14 Ibid.194 13 John D. Norton, “Thought Experiments in Einstein´s Work”, in Thought Experiments in Science and Philosophy, ed. Tamara Horowitz and Gerald Massey (Savage, MD: Rowman & Littlefield, 1991), 131 15 16 Kathleen V. Wilkes, Real People: Personal Identity Without Thought Experiments (Oxford: Clarendon Press, 2001), 43. 5 A thought experiments is only valid if: i. ii. iii. it can be reconstructed into an argument, the impossible parts of the argument can be eliminated, the background is described in a way that enable us to easily imagine the setting. The setting of the thought experiment itself can be as impossible as one wishes, as long as it does not hinder our capacity to imagine the situation. If we hold our thought experiments to this standard we will reduce the confusions we face in discourse in the topic of personal identity. This is by no means an easy process. There is a reason thought experiments are preferred over conventional argumentation. If we are in doubt, however, about whether a thought experiment succeeds, we can apply the formula above. Lasse Nielsen Department of Philosophy Katedra filozofie Filozofická fakulta UP Křížkovského 12 771 80 Olomouc E-mail: [email protected] 6