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.