Monday, 24 July 2017

Identity: From Theseus's Paradox to the Singularity

Posted by Keith Tidman

A "replica" of an ancient Greek merchant ship based on the remains of a ship that wrecked about 2,500 years ago.  With acknowledgements to Donald Hart Keith.
As the legend goes, Theseus was an imposing Greek hero, who consolidated power and became the mythical king of Athens. Along the way, he awed everyone by leading victorious military campaigns. The Athenians honoured Theseus by displaying his ship in the Athenian harbour. As the decades rolled by, parts of the ship rotted. To preserve the memorial, each time a plank decayed, the Athenians replaced it with a new plank of the same kind of wood. First one plank, then several, then many, then all.

As parts of the ship were replaced, at what point was it no longer the ‘ship of Theseus’? Or did the ship retain its unique (undiminished) identity the entire time, no matter how many planks were replaced? Do the answers to those two questions change if the old planks, which had been warehoused rather than disposed of, were later reassembled into the ship? Which, then, is the legendary ‘ship of Theseus’, deserving of reverence — the ship whose planks had been replaced over the years, or the ship reassembled from the stored rotten planks, or neither? The Greek biographer and philosopher Plutarch elaborated on the paradox in the first century in 'Life of Theseus'.

At the core of these questions about a mythical ship is the matter of ‘identity’. Such as how to define ‘an object’; whether an object is limited to the sum of people’s experience of it; whether an object can in some manner stay the same, regardless of the (macro or micro) changes it undergoes; whether the same rules regarding identity apply to all objects, or if there are exceptions; whether gradual and emergent, rather than immediate, change makes a difference in identity; and so forth.

The seventeenth-century English poilitical philosopher, Thomas Hobbes, weighed in on the conundrum, asking, ‘Which of the two existing ships is numerically one and the same ship as Theseus’s original ship?’ He went on to offer this take on the matter:
‘If some part of the first material has been removed or another part has been added, that ship will be another being, or another body. For, there cannot be a body “the same in number” whose parts are not all the same, because all a body’s parts, taken collectively, are the same as the whole.’
The discussion is not, of course, confined to Theseus’s ship. All physical objects are subject to change over time: suns (stars), trees, houses, cats, rugs, hammers, engines, DNA, the Andromeda galaxy, monuments, icebergs, oceans. As do differently categorised entities, such as societies, institutions, and organizations. And people’s bodies, which change with age of course — but more particularly, whose cells get replaced, in their entirety, roughly every seven years throughout one’s life. Yet, we observe that amidst such change — even radical or wholesale change — the names of things typically don’t change; we don’t start calling them something else. (Hobbes is still Hobbes seven years later, despite cellular replacement.)

The examples abound, as do the issues of identity. It was what led the ancient Greek philosopher Heraclitus to famously question whether, in light of continuous change, one can ‘step into the same river twice’—answering that it’s ‘not the same river and he’s not the same man’. And it’s what led Hobbes, in the case of the human body, to conveniently switch from the ‘same parts’ principle he had applied to Theseus’s ship, saying regarding people, ‘because of the unbroken nature of the flux by which matter decays and is replaced, he is always the same man’. (Or woman. Or child.) By extension of this principle, objects like the sun, though changing — emitting energy through nuclear fusion and undergoing cycles — have what might be called a core ‘persistence’, even as aspects of their form change.
‘If the same substance which thinks be changed,
it can be the same person, or remaining
the same, it can be a different person? — John Locke
But people, especially, are self-evidently more than just bodies. They’re also identified by their minds — knowledge, memories, creative instincts, intentions, wants, likes and dislikes, sense of self, sense of others, sense of time, dreams, curiosity, perceptions, imagination, spirituality, hopes, acquisitiveness, relationships, values, and all the rest. This aspect to ‘personal identity’, which John Locke encapsulates under the label ‘consciousness’ (self) and which undergoes continuous change, underpins the identity of a person, even over time — what has been referred to as ‘diachronic’ personal identity. In contrast, the body and mind, at any single moment in time, has been referred to as ‘synchronic’ personal identity. We remain aware of both states — continuous change and single moments — in turns (that is, the mind rapidly switching back and forth, analogous to what happens while supposedly 'multitasking'), depending on the circumstance.

The philosophical context surrounding personal identity — what’s essential and sufficient for personhood and identity — relates to today’s several variants of the so-called ‘singularity’, spurring modern-day paradoxes and thought experiments. For example, the intervention of humans to spur biological evolution — through neuroscience and artificial intelligence — beyond current physical and cognitive limitations is one way to express the ‘singularity’. One might choose to replace organs and other parts of the body — the way the planks of Theseus’s ship were replaced — with non-biological components and to install brain enhancements that make heightened intelligence (even what’s been dubbed ultraintelligence) possible. This unfolding may be continuous, undergoing a so-called phase transition.

The futurologist, Ray Kurzweil, has observed, ‘We're going to become increasingly non-biological’ — attaining a tipping point ‘where the non-biological part dominates and the biological part is not important any more’. The process entails the (re)engineering of descendants, where each milestone of change stretches the natural features of human biology. It’s where the identity conundrum is revisited, with an affirmative nod to the belief that mind and body lend themselves to major enhancement. Since such a process would occur gradually and continuously, rather than just in one fell swoop (momentary), it would fall under the rubric of ‘diachronic’ change. There’s persistence, according to which personhood — the same person — remains despite the incremental change.

In that same manner, some blend of neuroscience, artificial intelligence, heuristics, the biological sciences, and transformative, leading-edge technology, with influences from disciplines like philosophy and the social sciences, may allow a future generation to ‘upload the mind’ — scanning and mapping the mind’s salient features — from a person to another substrate. That other substrate may be biological or a many-orders-of-magnitude-more-powerful (such as quantum) computer. The uploaded mind — ‘whole-brain emulation’ — may preserve, indistinguishably, the consciousness and personal identity of the person from whom the mind came. ‘Captured’, in this term’s most benign sense, from the activities of the brain’s tens of billions of neurons and trillions of synapses.

‘Even in a different body, you’d still be you
if you had the same beliefs, the same worldview,
and the same memories.’ — Daniel Dennett
If the process can happen once, it can happen multiple times, for the same person. In that case, reflecting back on Theseus’s ship and notions of personal identity, which intuitively is the real person? Just the original? Just the first upload? The original and the first upload? The original and all the uploads? None of the uploads? How would ‘obsolescence’ fit in, or not fit in? The terms ‘person’ and ‘identity’ will certainly need to be revised, beyond the definitions already raised by philosophers through history, to reflect the new realities presented to us by rapid invention and reinvention.

Concomitantly, many issues will bubble to the surface regarding social, ethical, regulatory, legal, spiritual, and other considerations in a world of emulated (duplicated) personhood. Such as: what might be the new ethical universe that society must make sense of, and what may be the (ever-shifting) constraints; whether the original person and emulated person could claim equal rights; whether any one person (the original or emulation) could choose to die at some point; what changes society might confront, such as inequities in opportunity and shifting centers of power; what institutions might be necessary to settle the questions and manage the process in order to minimise disruption; and so forth, all the while venturing increasingly into a curiously untested zone.

The possibilities are thorny, as well as hard to anticipate in their entirety; many broad contours are apparent, with specificity to emerge at its own pace. The possibilities will become increasingly apparent as new capabilities arise (building on one another) and as society is therefore obliged, by the press of circumstances, to weigh the what and how-to — as well as the ‘ought’, of course. That qualified level of predictive certainty is not unexpected, after all: given sluggish change in the Medieval Period, our twelfth-century forebears, for example, had no problem anticipating what thirteenth-century life might offer. At that time in history, social change was more in line with the slow, plank-by-plank changes to Theseus’s ship. Today, the new dynamic of what one might call precocious change — combined with increasingly successful, productive, leveraged alliances among the various disciplines — makes gazing into the twenty-second century an unprecedentedly challenging briar patch.

New paradoxes surrounding humanity in the context of change, and thus of identity (who and what I am and will become), must certainly arise. At the very least, amidst startling, transformative self-reinvention, the question of what is the bedrock of personal identity will be paramount.


  1. I enjoyed the article very much. I do have views that are perhaps a little different than those expressed in the article. It is my view that nothing is the same, from one moment to another. While the atomic construction may be the same, the view of the object, its possible use, importance to the people or organizations involved varies almost by the minute. The interaction between two people follows the same rules, I believe.

    1. That would require us to say, for example, that your response changes all the time, that you yourself are not meaningfully 'one person', that our lovely website does not really exist! So, I think it is a dangerous line of argument really. We must cling to our notions of persisting identity.

  2. Thank you, Louis, for your observations.

    I suspect we’re actually quite close in outlook. I would agree, for example, that things are in a state of flux — in many cases only extraordinarily subtly and slowly, in other cases dramatically — for all sorts of reasons: the environment’s toll on things, the effects of aging, the arrow of entropy/time, the nature of internal dynamics, and other influences. The same goes for engine blocks, carpets, suns, institutions, trees, and kings.

    Other examples include how the cells in the human body undergo a replacement every several years, how epigenetics changes organisms by providing the grounds for genes to express themselves differently, how people’s frames of mind (cognitive, rational, and emotional dimensions) naturally morph — and much more, of course.

    The plank-by-plank deconstruction of Theseus’s ship serves as a handy metaphor for precisely that subtly of change and the concomitant issue of identity — whether the thing or person is still the same or different, and whether there’s a tipping point such that the type and amount of change eventually matters with respect to ‘identity’. Identity really being the heart of the essay.

    Hence, in some strict sense, and as I think you suggest, Louis, encounters between two people may not be precisely duplicable in all aspects — whether it’s outwardly evident or not. In that vein, I’d point back to the question of Heraclitus, which, if taken in its most broad context, is instructive: His famously asking whether one can step in the same river twice, and summarily answering that it’s ‘not the same river and he’s not the same man’. A far-reaching application of Heraclitus, therefore, would lead to your conclusion, Louis, that ‘nothing is the same, from one moment to another’ — without exception.

    Again, I would venture that we largely overlap — separated, if at all, by no more than a paper-thin gap. Thanks, meanwhile, for expressing your take on all this.

  3. It seems to me like an aspect of a debate which once raged amongst the pre-Socratics: namely, how something can be when, at the same time, it is becoming. Parmenides in particular considered that a thing cannot truly exist if it changes. The problem is still very much alive today.

    The paradoxes of Zeno, a student of Parmenides, provide us with some examples of the problem. Supposing, for instance, that I try to run a mile. This is impossible, joked Zeno -- for the reason that I must always reach the half way mark first -- but then the half way mark of the half way mark, and so on ad infinitum. Therefore I shall never reach the finish.

    Zeno was speaking of a world which, on the one hand, seems to be fixed before us in ‘snapshots’ -- yet on the other hand moves and changes in time. I would cast my lot with Louis P Solomon.

    1. "a thing cannot truly exist if it changes"

      I mean, this is true, 'in a sense' (as per Louis just too) but then "Nothing exists". The 'truth' is, of course, that nowadays, thanks to Heidegger, we know that "Nothing noths"!

    2. Dear Gentlemen,

      Abstractly referring to Derrida; when there is culture, nature cannot exist any longer, makes me wonder the following.
      When men has placed his identity in culture, how could identity find it’s place back into nature? The plank-by-plank changes to Theseus’s ship is symbolic for a scission that change does not conform to concepts that create culture.

    3. Regarding ‘When man has placed his identity in culture, how could identity find its place back into nature?’ My personal take, Tessa, is that in the realm of how and where to root one’s identity, culture and nature don’t exclude one another. It’s not, I suggest, either-or; rather, the two spheres compatibly overlap — perhaps not entirely so, but at the very least along the (crude) lines of a Venn diagram. Humankind’s intellect, imagination, creativity, and adaptability make it possible for one’s identity to be readily and appropriately anchored in both culture and nature simultaneously, with neither crowding out the other. In short, I suggest that, as to rooting one’s identity, culture and nature are compatible.

  4. Someone who read my post referred me to a Malcolm Gladwell podcast that describes how the principles of the Theseus Paradox were applied, in a rather curious fashion, to a major modern-day, real-world situation. The circumstance entailed the rationale behind California law minimising the tax liability of the state’s wealthy golf courses. State law freezes golf course property taxes at their 1978 level as long as the ownership doesn’t change. But, of course, defining ‘doesn’t change’ is key. Golf courses are collectively owned by the members, many of whom have died off or withdrawn over the several intervening decades. In fact, most California golf courses have only a tiny percentage of the same members from 1978. So, does that constitute a ‘change in ownership’, or not? The ruling, later reaffirmed as recently as 2010, was that slow, smooth, member-by-member change over the decades — analogous to Theseus’s ship’s planks being removed one-by-one over the years — conveniently didn’t qualify as a change in ownership under the law. That is, the fundamental essence of the whole (identity) remained intact — spatio-temporal continuity, if you will. There was no one single event. Gladwell’s podcast tells more: (Theseus’s Paradox enters the picture around the halfway point, though the lead-up informatively sets the stage.)

    1. It sounds more to me a dispute about the term rather than the content, if you see what I mean.If the golf course belongs to a special kind of owner known as 'the membership' then it still does even if the individuals who make up the 'membership' are all different. For example, the chess boards may belong to the Chess Club - and who cares who is actually a member of that at any particular time. The ship paradox is more compelling!

    2. An interesting interpretation, Martin. Looking at ‘the membership’ as a whole — its being the prevailing entity as to identity — regardless of the comings and goings (largely goings) of individuals that made up the original membership is certainly one possible takeaway. It reminds me, if imperfectly, of Mitt Romney’s blurting out to a heckler in 2011, as part of his presidential campaign, that ‘corporations are people, my friend’. It appears — unsurprisingly — that the paradox remains a paradox.