Trigger’s broom and the identity of persons over time

“Trigger” was always my favourite inhabitant of Only Fools and Horses, John Sullivan’s alternative Peckham. In researching this piece I’ve discovered that the fictional road sweeper’s real name was “Colin Ball” and that his father, according to Trig, “died a couple of years before I was born”. Why did he always call Rodney “Dave”? This is a deep mystery, one which is beyond the scope of this piece, which will limit itself to discussion of the nature of persons, identity, and time.

Which brings us to the conundrum of Trigger’s broom, which in the course of 20 years has had 17 heads, and 14 new handles. How can he be sure it’s the same broom? Easy: he has a photograph of it. 

We laugh but why isn’t it the same broom? Sullivan here is referencing a metaphysical complexity, one which was most famously raised by the first century essayist and biographer Plutarch:

“…The thirty-oared ship in which Theseus sailed with the youths and came back safe was kept by the Athenians up to the time of Demetrius Phalereus. They constantly removed the decayed part of her timbers and renewed them with sound wood, so that the ship became an illustration to philosophers of the doctrine of growth and change, as some argued that it remained the same, and others, that it did not…” – Theseus, 23.

How does an object which is continually being replaced retain an identity over time? The universe is in a continual state of flux, static only to the mind of He who overlooks it. So, what makes something the same thing now as it was five minutes ago? If “change” is the primary universal mechanism, then whence comes stability?

 And, more consequentially perhaps, what makes somebody the same person on a Tuesday that they were on the previous Wednesday?

The philosopher John Locke (1632-1704) noticed that it is logically possible that the history of the body might not be the same thing as the history of the person who “inhabits” that body. The “identity criteria” which can apply to a physical object – exploiting the fact that it is locatable in space and in time — do not necessarily apply to a “self” which seems to exist non-spatially. In Dickens’s Hard Times, Mrs Gradgrind remarks that there’s a pain in the room somewhere, but she can’t be certain who it belongs to. Her remark seems deeply odd because it applies to the human soul those laws of physics which can only properly be applied to physical bodies; it’s a sort of category error.

Locke’s solution was to propose that it is memory which acts as a guarantor of personal identity over time, but this is to beg the question. For it is always possible to ask who it is that is doing the remembering.

It is an assumption that there is some “fact of the matter” that guarantees that you are the same person today as you were yesterday. What if there isn’t? In his Reasons and Persons, the philosopher Derek Parfit (1942-2017) deploys a series of thought experiments intended to subvert the intuition that we retain a personal identity across time. Parfit’s project is a sort of “metaphysics meets Star Trek”.

Imagine you step into a “teleportation” machine, which annihilates every molecule of your body while beaming a set of protocols to another machine (at the speed of light), instructing that machine to replicate those molecules. Is the consequent individual you or not? It might seem to you that you have travelled from one machine to the other. But an alternative explanation might be that a new “you” has been created, one with the memories of the old one. 

Which explanation is the correct one? Is Scotty really “beaming up” Captain Kirk? Or is he destroying this Kirk and creating a new one?

Parfit’s conclusion is that there is no way of adjudicating between those two ways of looking at the situation. His conclusion is a deflationary one: we need to stop thinking about our “selves” now as being identical to the “selves” we were previously, and those we will evolve into. 

This seems esoteric but Parfit’s conclusion, if true, has serious ethical consequences. If I am not strictly speaking identical to my “future self”, then I have obligations to that person in the same way that I have obligations to my neighbour. Should I smoke, given that it might be damaging to a future person not strictly identical with myself? We accept, most of us, that we have obligations to future generations. Should we concede, also, that we have obligations to our future selves?

I’ll say two things against Parfit’s project. First, it should be acknowledged that his system is developed outside any theological framework. It is secular and reductionistic. Other brands are available.

Second, there is always the danger with philosophy-by-thought-experiment that you end up confusing what is conceivable with what is actually possible. Robert Heinlein’s brilliant short story All You Zombies platforms a series of time travel thought experiments. The story’s “reveal” is that the protagonist turns out to be himself, his father, and his mother. Is that conclusion paradoxical? Or flat-out contradictory?

So, to return to the paradox of the broom. Is Trigger right or wrong? Let’s at least acknowledge that if he is wrong then his mistake, funny as it is, is merely an amplification of an error most of us habitually fall into.

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