Causation and personal identity

Michael asked:

I have a question about personal identity, specifically theories that rely upon causal continuity.

I recently came across an objection that I haven’t seen before and this is my attempt to reconstruct it.

1. Theories of Personal Identity rely upon causal continuity, specifically theories such as Psychological Continuity Theory.

2. We stand in causal relationships with other people as well. For example, causing them to feel emotions or remember events.

3. We bear no relationship with the people we are in casual relationship with. I.e. I’m not identical my dad whom I caused to remember his birthday.

4. Therefore, causal connections cannot ground personal identity.

This was a very brief argument I read in a paper, and I was trying to figure out its validity and how to respond to it. Thank You.

Answer by Geoffrey Klempner

To fully answer your question I would have to write a book — which I am not going to do! However, I will try to unpick the main strands of argument.

There is a theory, proposed in the 18th century by John Locke, which holds that psychological continuity is all there is to personal identity. Locke was a mind-body dualist, but argued in a thought experiment (the Prince and the Pauper) that you and I could switch ‘souls’ without either of us being aware of that fact. I am still GK and you are still Michael. In other words, psychological continuity is all that is necessary and sufficient for personal identity.

The main objection to this from David Wiggins (Identity and Spatio-Temporal Continuity, Sameness and Substance) is that Locke fails to distinguish ‘genuine’ memory from mere ‘seeming’ memory.

For example, I wake up tomorrow morning convinced that I am Napoleon. Under exhaustive questioning, amazingly I am able to ‘remember’ lots of things about Napoleon’s life that no-one could possibly know. It’s nothing short of miraculous. Well, maybe it is just a miracle, or possibly a massive fluke aided by my vivid imagination. What would make the difference, Wiggins would say, is if there is continuity in an organized package or bundle of ‘all that is causally necessary and sufficient’ for my seeming memories of Napoleon to be genuine memories. For that, I would have to possess Napoleon’s physical brain.

In common with many theories of personal identity, there is a problem of ‘splitting’, as in Sydney Shoemaker’s famous ‘split brain’ thought experiment. In a ‘Star Trek’ episode, one of the crew members, Riker, is ‘beamed down’ to a planet but owing to a glitch, two identical Rikers materialize. I’m happy to say that both persons are Riker. They share life histories up to the point when the transmitter beam was switched on. In principle, there could be a thousand or a million Rikers populating the planet, each and every one of them was born at the same time, in the same place, conceived from the same sperm and egg.

David Lewis argues for this view, but it is not that popular. Wiggins rejects it on the grounds that it makes talk of ‘identity’ almost meaningless, but we can bring in Locke here, arguing that personal identity is a ‘forensic’ concept. If Riker committed murder before being beamed down then both Rikers fully deserve to be punished, don’t they? It doesn’t seem to matter whether or not the physical ‘stuff’ of Riker is preserved in the process of beaming down. Let’s say there are pots of ‘people stuff’ waiting to be used to make physical copies of Riker’s body. The body of the original Riker was destroyed.

Well, maybe the concept of personal identity is merely a convenience. Maybe the very idea that punishment is ‘deserved’ or not is questionable (an issue that also arises in connection with the free will debate). However, it would not follow that my causing you to have a belief that P would somehow entail problems with the causal account. I wake up in the morning hearing a familiar patter on the roof and form the belief that it is raining. You phone me up and ask what’s the weather like here. I say ‘It is raining,’ and now you believe this too. But the causal link in either case is completely different.

Up until a few years ago, I would have been happy to give a version of this theory. Now I am not. I no longer accept that the physical facts whatever they may be are sufficient for identity. Causation, conceived a physical instance falling under a causal law, is not sufficient. Why? Because ‘I might not have existed but someone exactly like me might have existed in my place’ (as in my book of the same title). The thing I call ‘I’ might or might not have come into existence five seconds ago. If I came into existence five seconds ago, no-one, including me, would ever know. But there is an answer to that question — in ‘ultimate reality’.

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