In this discussion over at Edge, Joshua Knobe presents some recent findings of experimental philosophy on the problem of personal identity. Experimental philosophy, which sounds oxymoronic, is the new and trendy (if it still is?) fashion for philosophising rooted in actual experiments, often of a psychological nature. The examples I’ve read have all been perfectly acceptable and useful – and why shouldn’t they be? No one ever said philosophy couldn’t be inspired by science, or draw on science. In this case, though, I was not altogether convinced.
After a few words about the basic idea of experimental philosophy, Knobe introduces a couple of examples of interesting problems with personal identity (as he says, it is one of the longer-running discussions in philosophy of mind, with a much older pedigree than discussions of consciousness). His first example is borrowed from Derek Parfit:
Imagine that Derek Parfit is being gradually transformed molecule by molecule into Greta Garbo. At the beginning of this whole process there’s Derek Parfit, then at the end of the whole process it’s really clear that Derek Parfit no longer exists. Derek Parfit is gone. Now there’s Greta Garbo. Now, the key question is this: At what point along this transformation did the change take place? When did Derek cease to exist and when did Greta come to exist? If you just have to reflect on this question for a while, immediately it becomes clear that there couldn’t be some single point — there couldn’t be a single second, say – in which Derek stops existing and Greta starts existing. What you’re seeing is some kind of gradual process where, as this person becomes more and more and more different from the Derek that we know now, it becomes less and less right to say that he’s Derek at all and more and more right to say that he is gone and a completely other person has come into existence.
I’m afraid this doesn’t seem a great presentation of the case to me. In the first place, it’s a text-book case of begging the question. The point of the thought-experiment is to convince us that Parfit’s identity has changed, but we’re just baldly told that it has, right from the off. We should be told that Parfit’s body is gradually replaced by Garbo’s (and does Garbo still exist or is she gradually eroded away?), then asked whether we still think it’s Parfit when the process is complete. I submit that, presented like that, it’s far from obvious that Parfit has become Garbo (especially if Garbo is still happily living elsewhere); we would probably be more inclined to say that Parfit is still with us and has simply come to resemble Garbo – resemble her perfectly, granted – but resemblance is not identity.
Second: molecule by molecule? What does that even mean? Are we to suppose that every molecule in Parfit has a direct counterpart in Garbo? If not, how do we choose which ones to replace and where to put them? What is the random replacement of molecules going to do to Parfit’s DNA and neurotransmitters, his neurons, his capillaries and astrocytes? Long before we get to the median sage Parfit is going to be profoundly dead, if not reduced to soup. I know it may seem like bad manners to refuse the terms of a thought experiment; magic is generally OK, but what you can’t do is use the freedom it provides to wave away some serious positions on the subject – and it’s a reasonable position on personal identity to think that functional continuity is of the essence. ‘Molecule by molecule’ takes it for granted that Parfit’s detailed functional structure is irrelevant to his identity.
In fairness we should probably cut Knobe a bit of slack, since circumstances required a short, live exposition. His general point is that we can think of our younger or older selves as different people. In an experiment where subjects were encouraged to think either that their identities remained constant, or changed over time, the ones encouraged to believe in change were happier about letting a future payment go to charity.
Now at best that tells us how people may think about their personal identity, which isn’t much help philosophically since they might easily be flat wrong. But isn’t it a bit of a rubbish experiment, anyway? People are very obliging; if you tell them to behave in one way and then, as part of the same experiment, give them an opportunity to behave that way, some of them probably will; that gives you no steer about their normal behaviour or beliefs. There’s plenty of evidence in the form of the massive and prosperous pensions and insurance industries that people normally believe quite strongly in the persistence of their identity.
But on top of that, the results can be explained without appealing to considerations of identity anyway. It might be that people merely think: well, my tastes, preferences and circumstances may be very different in a few years, so no point in trying to guess what I’ll want then without in any way doubting that they will be the same person. Since this is simpler and does not require the additional belief in separate identities, Occam’s Razor tells us we should prefer it.
The second example is in some ways more interesting: the aim is to test whether people think emotional, impulsive behaviour, or the kind that comes from long calm deliberation, is more truly reflective of the self. We might, of course, want to say neither, necessarily. However, it turns out that people do not consistently pick either alternative, but nominate as the truest reflection of the person whichever behaviour they think is most virtuous. People think the true self is whichever part of you is morally good.
That’s interesting; but do people really think that, or is it that kindness towards the person in the example nudges them towards putting the best interpretation possible on their personhood – in what is actually an indeterminate issue? I think the latter is almost certainly the case. Suppose we take the example of a man who when calm (or when gripped by artistic impulses) is a painter and a vegetarian; when he is seized by anger (or when thinking calmly about politics) he becomes a belligerent genocidal racist. Are people going to say that Hitler wasn’t really a bad man, and the Nazism wasn’t the true expression of his real self; it was just those external forces that overcame his better nature? I don’t think so, because no-one wants to be forgiving towards Adolf. But towards an arbitrary person we don’t know the default mode is probably generosity.
I dare say this is all a bit unfair and if I read up the experiments Knobe is describing I should find them much better justified than I suppose; but if we’re going to have experiments they certainly need to be solid.