Ten years the same, ten years different

Every ten years each of us becomes Theseus' ship, or a ship of sorts. Allow me to clarify what I mean by this. Legend has it that the famous ship sailed by the hero Theseus was kept in a dry dock, prefiguring what we do with some museum pieces, for all to behold the vessel that had enabled so many feats of prowess. Plutarch wrote in this piece (nicely translated by John Dryden) that as some of the ship's planks started to rot they were replaced, and that year after year all of the original planks had been replaced so that it was logical for some to contend the very existence of Theseus' ship. If no original piece remains, it can't be the same ship, can it?

To cut a very long story short, the issue has been debated up until now, and is likely to remain so for a long time. It didn't help that Thomas Hobbes introduced a spin-off to the story (in De Corpore, 1655): the Athenians who replaced the rotten planks didn't have the heart to throw them away, but kept them in a dry place for future generations to manage. Imagine now that these future generations repaired the rotten planks and reassembled the ship to its original form. Which one would be the “real” ship of Theseus?

You might have seen me coming by now: it's sort of the same thing with us. It is now common knowledge that many, many cells in our body have a life span, that they die and are replaced in a continuous cycle. In just a few days our intestines will have renewed themselves completely. Taste buds in ten to fifteen days. It takes two weeks to a month for our body to renew its skin cells entirely. Same for our lungs. Liver cells renew in a few months (four or so). Every three to six years not a single hair on our head is the same. Bones take a decade to regenerate, while studies show that the stem cells in the heart are replaced over the course of twenty years or so.

So...are we still the same? If our entire body is completely renewed in the course of ten years, we can't really be the same “us”, can we? A person aged eighty will have shed its body eight times over, like a spider shedding its casing so it can grow. Those who are keen to question the ontological paradox cannot ignore that this comes with some caveats: only the cornea in your eyes renews its cells, the rest of the eye is the “same” age as you are. The brain doesn't renew anything during its lifespan – which therefore corresponds to your lifetime. So it must be something else.

Heraclitus proposes to answer this by taking the analogy of the river: if you step in a river one day, and you step in the same river many years later, neither the river nor yourself will be the same. The drops of water will have been long gone into the sea, and you will have experienced events which will have changed you. The key here is experience: life events change our frame of mind, our perspective and outlook on life, death and other matters. In a way, we're never ourselves entirely and fully as we constantly change.

So...no self, ever? As per usual, it's a tad more complex: our identities may change and shift over time, our bodies may not entirely be the same as our cells renew themselves, as we acquire scars. Epigenesis postulates that even though the DNA sequence is the same in every cell, our genome changes over time, epigenetic markers bearing witness to the thrives and throes of any individual's life. (Long aside here: epigenesis is a fascinating subject, I can't recommend enough that you research it for yourself...and initially I didn't want to give any pointer as I didn't want to influence anyone on this particularly hot topic, but as it's a vast and complex issue I could recommend reading this article, perhaps this one too which is less technical, and researching Lamarck, Weissmann, and Lyssenko.) In a nutshell, all the environmental changes around you which influence in one way or another your way of living, or your diet, or the need to be warm or look for colder climes etc. will leave a chemical mark in your genome, to be passed on – or not – to future generations.

Hang on, so now you're telling us that every ten years we're different all over? Well, no. Schrödinger and Heisenberg would probably frown at this, and each for different reasons, but it is theoretically possible for an object to be in two states, or for this object's state to be indeterminable, at the same time. The ship could be in two locations at the same time because if A = B and B = C then A= C, or nowhere at the same time because the ship doesn't matter, as A ≠ B and B ≠ C then A ≠ C (ergo, there is no ship). The key question here is: is reality dependent on the observer, or is it true at any time and place, regardless of whether or not people measure and attribute meaning to the thing observed? If you change every single member of your favourite football team, is it still the same team you're supporting year in and year out? That's because we attribute more internal “meaning” than what science tells us there initially is (actually science tells us that there can be no internal meaning as there might be no external meaning).

Chomsky would probably agree that our definition of “the same” is screwed because our outlook is skewed. The two ships, our bodies (rather, the different aspects of our body over time), are qualitatively identical, not numerically so. He would also gloss that we, poor human beings with limited senses and perception, externalise some of what we believe to be ontologically true onto the physical world. Our gut feeling (aka intuition) tells us this or that ought to be true but cognitively speaking we're mistaken. Same goes with Theseus' ship exemplifying our double standards. Imagine the ship in a museum: the whole ship is labelled “Original Ship of Theseus”, parts are labelled “Original bed”, “Original linen”, “Original rudder”. Some planks have been replaced: still the same ship. Most planks have been replaced: same ship. All of them: same ship. Rudder need be replaced: well, not original rudder any more...fake news! Changed linen: change the label! Do parts compose the whole? Is the whole whole even if it's no longer whole?

Perhaps the conundrum should be put differently, within a tighter set of boundaries. Being or remaining the same or different remains a valid line of questioning if we pluralise our approaches and don't consider one set of variables to be the only one worth examining. For our brains will tell us different things at different times. It might tell us that the original ship is waiting to be reassembled, and we will have to use the same elements, down to the same nails. But even if we use the same techniques as back then, would your brain tell you it's (finally!) the real ship of Theseus? How could we know? What if Theseus' crew had to change parts of the “original” ship while on board? Do we have to redefine 'original' even after every repair? Do we have to question and redefine our selves every ten years? Every other month? Is identity an ever-shifting concept, never to be grasped? What is right: our senses, our intuition, natural sciences, philosophy, quantum theory?

I'll leave you with one such theory: would it be utterly nonsensical to figure ourselves one object at a particular point of space and time, and then agree that this is “me” or “Theseus' ship”, and then agree further that this “me” is also “me” at a different point in space and time, and that these “mes” are just multiple covariants of “me”? Part and parcel of the same equation? A set of coordinates doesn't mean anything per se, and differentials can only acquire meaning if the frame of reference remains within the bounds of what we designate as 'reality'.

The answer, if there needs to be any, follows the same differential path: it shifts according to the tools with which its components are examined, and possibly lies in more than one frame of reference.