Perspective on Theseus

Chump in Chief* wrote a piece on dementia using analogue of the ship of Theseus. As a topic, Hobbes’** Theseus thought experiment has been well-covered, but that’s never stopped me before.

This is all about identity. Essentially, there are two perspectives. To an observer not on the ship or aware of the transformation, they would be none the wiser. For all intents and purposes, if they had ever seen the ship before, it’s the same. But what about those on the ship?

For nearly all of these observers, it’s almost unquestionably still the same ship. In a manner paralleling a person’s cells being sloughed off every 7 years, the cells in place at the start aren’t there after 7 years. Most will not doubt that you are the same person.

the average human cell is about 7 to 10 years old

As cells are continually dying and replacing themselves, for an adult the average human cell is about 7 to 10 years old, which might be interpreted as saying in the fashion of Theses’ ship that a person is anew each 7 to 10 years. Let’s ignore that this is an average, and many cells have a lifespan of only a few days whilst others—cerebral cells in particular—are here from the start and so are as old as the person.

Another perspective is to consider the replacement parts: would it matter if the colour of the parts changed in the process? What about the materials? What about the underlying architecture? What if the departing sloop arrived a schooner? Weight? What then?

My favourite extension of this thought experiment is to ask the question two-fold: Not only do we ask if this ship built with new materials is still Theseus’ ship—which to be fair is more a question of ownership than of identity—, but what if I reconstruct the original ship with the original materials. Are these both Theseus’ ships? Can we continue this exercise with new material ad infinitum?

As far as I know, we can’t repurpose cells in this fashion, but what if we could? There are many such Star Trek transporter mishap thought experiments, or the Duplicates Paradox.

In these experiments, a transporting device disintegrates the subject, and replicates the subject at a distance—but this replication presumably uses different atoms and cells, and so what if a duplicate copy is made rather than the replacement copy? Who’s identity prevails? Is it murder to eliminate one of the duplicates? Similar questions have played out in the science fiction / fantasy space.

Locke and others suggest that for people, memory and the continuity of thought are key, but your thoughts of me are not the same as my thoughts of me. This is why an amnesiac may no longer maintain some original identity, and yet to the familiar outside observer, this shell of a person remains intact. This is pretty much how it plays out with zombies and dementia patients. This sense of identity is projected upon the person rather than exuded from them.

So what is my perspective? Rather than a paradox, it is more a problem of vaguity or ambiguity and how we’re defining sameness. There are many dimensions to similarity. I can present you a red square, a green square, a blue triangle, and a green triangle and play the Sesame Street ‘one of these things is not like the other game.

Is the sameness the colour, the shape, or the number? Could one be comparing area or perimeter?

So, I’ve gone off the reservation. I don’t put a lot of weight in notion of identity. It has evolutionary merit and is an effect of humans’ nature (as it were) to categorise and taxonomise.

* This Chief Chump charge may be unwarranted or even understated, as I don’t know this bloke.
** This is the same Hobbes with the ‘solitary, poor, nasty, brutish, and short’ claim to fame.