Shapeshifters, Socks, and Personal Identity

Posted by Martin Cohen

Perhaps the proudest achievement of philosophy in the past thousand years is the discovery that each of us really does know that we exist. Descartes sort-of proved that with his famous saying:

"I think therefore I am."

Just unfortunate then, that there is a big question mark hanging over the word ‘I’ here – over the notion of what philosophers call ‘personal identity’. The practical reality is that neither you nor I are in fact one person but rather a stream of ever so slightly different people. Think back ten years – what did you have in common with that creature who borrowed your name back then? Not the same physical cells, certainly. They last only a few months at most. The same ideas and beliefs? But how many of us are stuck with the same ideas and beliefs over the long run? Thank goodness these too can change and shift.

In reality, we look, feel and most importantly think very differently at various points in our lives.

Such preoccupations go back a long, long way. In folk tales, for example, like those told by the Brothers Grimm, frogs become princes – or princesses! a noble daughter becomes an elegant, white deer, and a warrior hero becomes a kind of snake. In all such cases, the character of the original person is simply placed in the body of the animal, as though it were all as simple as a quick change of clothes.

Many philosophers, such as John Locke, who lived way back in the seventeenth century, have been fascinated by the idea of such ‘shapeshifting’, which they see as raising profound and subtle questions about personal identity. Locke himself tried to imagine what would happen if a prince woke up one morning to find himself in the body of a pauper – the kind of poor person he wouldn’t even notice if he rode past them in the street in his royal carriage!

As I explained in a book called Philosophy for Dummies – confusing many readers – Locke discusses the nature of identity. He uses some thought experiments too as part of this, but not, by the way (per multiple queries!) the sock example. He didn't literally wonder about how many repairs he could make to one of his socks before it somehow ceased to be the original sock. He talks, though about a prince and a cobbler and asks which ‘bit’ of a person defines them as that person?

In a chapter called ‘Of Identity and Diversity’ in the second edition of the Essay Concerning Human Understanding, he distinguishes between collections of atoms that are unique, and something made up of the same atoms in different arrangements.

Living things, like people, for example, are given their particular identity not by their atoms (because each person's atoms change regularly, as we know) but rather are defined by the particular way that they are organised. The point argued for in his famous Prince and the Cobbler example is that if the spirit of the Prince can be imagined to be transferred to the body of the Cobbler, then the resulting person is ‘really’ the Prince.

Locke’s famous definition of what it means to be a ‘Person’ is:

‘A thinking intelligent being, that has reason, and can consider it self as it self, the same thinking thing, in different times and places; which it does only by that consciousness, which is inseparable from thinking’

More recently, a university philosopher, Derek Parfit, has pondered a more modern–sounding story, all about doctors physically putting his brain into someone else's body, in such a way that all his memories, beliefs and personal habits were transferred intact. Indeed today, rather grisly proposals are being made for ‘transplants’ like this. But our interest is philosophy, and Derek’s fiendish touch is to ask what would happen if it turned out that only half a brain was enough to do this kind of ‘personality transfer’?

Why is that a fiendish question to ask? But if that were possible, potentially we could make two new Dereks out of the first one! Then how would anyone know who was the ‘real’ one?!

Okay, that's all very unlikely anyway. And yet there are real questions and plenty of grays surrounding personal identity. Today, people are undergoing operations to change their gender – transgender John becomes Jane – or do they? Chronically overweight people are struggling to ‘rediscover’ themselves as thin people – or are they a fat person whose digestion is artificially constrained? Obesity and gender dysporia alike raise profound philosophical, not merely medical questions.

On the larger scale, too, nations struggle to decide their identity - some insisting that it involves restricting certain ethnic groups, others that it rests on enforcing certain cultural practices. Yet the reality, as in the individual human body, is slow and continuous change. The perception of a fixed identity is misleading.

“You think you are, what you are not.” 

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* The book is intended for introducing children to some of the big philosophical ideas. Copies can be obtained online here: https://www.createspace.com/6299050