An answer to the problem of Identity.

I'm not quite sure what A. C. Grayling was seeking to achieve in his latest piece for New Scientist Brain science and the search for the self because after a beautiful build-up he suddenly stopped and enjoined his readers to head off to the review of The Ego Tunnel on page 44, which lack of a proper conclusion to his own piece was a bit of a let down: I want to hear what Grayling has to say in Grayling's column - if I also I want to read a book review I can do that too.

Grayling has been writing for New Scientist since 2007, when he and Lawrence Krauss became columnists. Krauss, being primarily a scientist, has reaped the wrath of the readership on more than one occasion (see e.g. The free lunch that made our universe) for apparently taking the relaxed forum of a popular science column a little too lightly (notwithstanding the fact that New Scientist has described itself as a magazine "of ideas" rather than a science magazine), but Grayling has generally fared better. However, just as Krauss was rightly upbraided for posing the question "Why..." - the very posing of which implied a newly discovered answer of revelatory significance - then ditching "Why?" in favour of "How..." - whose answer was far, far less interesting, Grayling also needs a gentle rebuke for leading the readership up the garden path (although it was a very pretty walk).

OK, wrist slapping over, let's return to what Grayling actually wrote. The issue was the problem of "personal identity", which first came to prominence in Western philosophy in the work of John Locke, in his Essay Concerning Human Understanding in the chapter Of Identity and Diversity.

The question of the continuity of identity - and personal identity in particular - has been a constant irritant ever since, and, as philosophers are wont to do they have constructed a number of "problem cases" to highlight the difficulties. Such cases include The Ship of Theseus and Bernard Williams' consideration of the apparent duplication of Guy Fawkes (but in passing, let me also say how much I have appreciated Peter Unger's work on personal identity), but to skip ahead (I'll come back to the problem cases later) the whole point of this post is to suggest an answer (and another perspective on the questions "Who am I?" and "Who are you?")

And that answer is: given the numerous criteria that might be applied for determining personal identity and the usually conflicting answers obtained by applying them, the decisive factor in determination of personal identity should be the intended application of the answers obtained, i.e. the choice of criteria to employ (and hence the utility rather than validity of the answers) should be dictated by what we intend to do with the information obtained.

For example, let's consider the Guy-Guy, Fawkes-Fawkes problem - I'll restate the general idea in my own words rather than follow Williams' original presentation.

Suppose that we are presented with two people who both claim to be Guy Fawkes, the infamous expediter of the Gunpowder Plot episode of English history. Now having died in 1606 (apparently having escaped the disembowelling and quartering parts of his sentence) his reappearance over 400 years later presents significant challenges (to understate the position ever so slightly) for our understanding of biology, physics... well, for our understanding full stop I suppose. But let us suppose that, regardless of how improbable it might seem, we decide to determine formally whether either of the two likely pretenders is in fact Guy Fawkes.

Both men look like Guy Fawkes; under questioning by scrupulous historians, both are equally accurate in their apparent recollection of their past lives; DNA testing, using a lock of (the dead) Fawkes' hair as reference shows not only are both men genetically identical, they are also indistinguishable from the original Guy Fawkes where the original DNA was sufficiently well preserved to permit comparison. If there had been only one of them, it would have been almost unreasonable to deny his identity, the obstacle to identification in the case as stated is the duplication.

Had the death of Fawkes not been well attested and the conundrum was being addressed in say 1609 rather than 2009 (therefore of course neglecting the DNA evidence) we would almost certainly have said that one of the two men was Fawkes and the other was an imposter. But after 400 years of gentle mouldering, being unable to conceive how such a thing could be, we would be reluctant to identify either man as Guy Fawkes - however, even if we did allow the possibility that he had somehow returned, they can't both be Guy Fawkes: a central element of our consideration of personal identity is that of uniqueness. And yet all the evidence says otherwise... how are we to resolve the issue?

Firstly, if we can't understand how one Fawkes could reappear, our manifest ignorance should at least allow us to shrug and say, "Well - if one, why not two?", but that does not answer the question as to whether the two men are Guy Fawkes. To which the simple answer I wish to suggest is that they were both Guy Fawkes while at the same time making it explicit that I have no idea how to characterise who they are now: we simply don't have the concepts or language to describe the evolution of personal identity because it is counter to the fundamental concepts of uniqueness, continuity, and so forth. All references to "who we are" point to the past.

But if we accept that they were Guy Fawkes we could learn a lot from them - their complete DNA could be examined for genetic indicators of a disposition to violence, for example, or for genealogical purposes that the damaged DNA recovered from the dead Fawkes might not have supported; we could fill in the gaps of our historical understanding of events at the turn of the 17th century and so on.

But suppose now (Scenario B) that upon examination of Guy-Guy, Fawkes-Fawkes we find that one is apparently genetically identical with the original but remembers nothing of Fawkes' past, while the other is genetically unrelated and yet has incontrovertibly accurate knowledge of Fawkes' life and times.

Physical sameness (if not strict continuity) would suggest we should accept the former as Fawkes and dismiss the latter as an imposter, but continuity of identity through memory etc. would suggest the reverse. Which, if either, "is" Guy Fawkes?

That really, really irritating question "Who are you?" - as magnificently irritatingly as it was posed by Jack Nicholson (as Dr Buddy Ryell) to Adam Sandler (as Dave Buzni, the neurotic in need in the film Anger Management) - is the heart of the problem. The exchange is something like this....

Buddy: So, Dave... tell us about yourself. Who are you?
Dave: Well, I am an executive assistant... at a major pet products company.
Buddy: I don't want you to tell us what you do. I want you to tell us who you are.
Dave: All right. I'm a pretty good guy. I like playing tennis on occasion....
Buddy: Also, not your hobbies, Dave, just simple: Tell us who you are.
Dave: I just.... Maybe you could give me an example of what a good answer would be.
Buddy: What did you say? You want Lou to tell you who you are?
Dave: No, I just.... I'm a nice, easygoing man. I might be a little bit indecisive at times.
Buddy: Dave, you're describing your personality.

and so on. What's the right answer to the question "Who are you?"?

I suggest you make up your own (my own answer involves violence and is not to be recommended); the question is - if taken literally - unanswerable, so you might as well please yourself. (Ditto "What's the difference between a duck?" and "Why a mouse when it spins?"; there is however an answer to "What is the sound of one hand clapping?" - but that also involves violence).

The legitimate uses of the question are to place the person questioned in a context that the asker might recall, recognise - the personhood, life history, inner musings, etc. are irrelevant.

Useful, sensible, normal:

Knock Knock.
Who are you?
The pizza boy!

Unhelpful, disturbing, and more like me on a bad day

Knock Knock.
Who are you?
The man who as a child liked to weld glass with the electric arc produced by a salvaged Extremely High Tension power supply from an old television, who, through a sequence of events that need not concern us now, is currently employed as a pizza delivery boy and has the pizza he has reasonable grounds for believing you recently ordered.

Thus the question, "Which of our pair is the real Guy Fawkes?"should be seen as meaningless - there is no is-ness in identity, there is only was-ness.

Which brings us back to the Ship of Theseus (random Athenian trireme illustrated); to quote from Wikipedia the origin of the paradox:

According to Greek Legend as reported by Plutarch,

The ship wherein Theseus and the youth of Athens returned [from Crete] had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.

—Plutarch, Theseus^[1]

Plutarch thus questions whether the ship would remain the same if it were entirely replaced, piece by piece. As a corollary, one can question what happens if the replaced parts were used to build a second ship. Which, if either, is the original Ship of Theseus?

Since no two things presented to us are or could ever be strictly, exactly, precisely identical - two otherwise identical apples presented to us necessarily differ in their position - we implicitly address identicalness in terms of unstated criteria. The question of identity is usually that of identity across time - is this the same tree as yesterday, for example - in which case we are unable to compare the two instances "side by side". We must accept the imperfection of our knowledge of the state of yesterday's tree and rely on certain proxies, for example trees don't move from place to place and therefore, all other things being equal the tree here today is yesterday's tree.

In the case of the Ship of Theseus we are however presented with explicit alterations - the replacement of rotten timbers - that are merely the unavoidable changes of life (the shedding and the growth of hair, skin; the flow of water and other materials through out bodies) writ large. But if we are explicit about the criteria of identity the problem disappears.

To the archaeologist who unearths Theseus' barque, the timbers will show the shape, the design, etc. but they would not allow him to determine precisely when the ship was first built. Theseus' ship as preserved is the Ship of Theseus in this significant way, but it is not identical with the ship at the time of launch. If all the replaced timbers could be collected together again and re-assembled the result would also "be" the Ship of Theseus. And just as we objected to Guy-Guy, Fawkes-Fawkes both being "Guy Fawkes" on the basis that there cannot be two things the same as one previous thing (which we might characterise as the Principle of the Conservation of Identity) we are also obliged to ask which is the real ship or to state that neither is.

The answer is of course that they both were the Ship of Theseus - and now they are something else. Such duplication just cries out for a new label, so let us refer to instances of an entity as an Incarnation. Given two Incarnations of Theseus' ship, neither "is" The ship, but the two incarnations may equally lay valid claim to having been The ship. Ditto Guy-Guy, Fawkes-Fawkes - what we need to do in expressing identity is to be clear about the relevant characteristics... for the purposes of X, A & B may be identical, but for purpose Y they could be non-identical.

I think that's enough for now.

... The Same Old Stuff