Work Text:
Stanford Encyclopedia of Philosophyagain.☼again.☼
The Ship of Theseus
- First published Thur Jan 2, 2025
- Footnotes added Tues Jan 7, 2025
- Additional footnotes Mon Jan 13, 2025
The Ship of Theseus (or "Theseus's Paradox") is a philosophical paradox the identity of something after it undergoes repeated changes. whether something retains its identity over multiple small changes. It is named for a ship that has its boards replaced one by one, until no part of the original vessel remains. The paradox has relevance not only to physical objects, but also to any kind of pattern that can have gradual change, such as artwork, social movements, and personal identity.
considering1concerning☼
1. Mythological Origins
While questions of identity date back to the beginnings of philosophy itself, the Ship of Theseus, as an emblem for ambiguous identity, has its origins in Greek mythology. gradual mutation of identity, refers to a particular ship in Athenean history.
the question of 2the problem of☼
The hero Theseus features prominently in Greek mythology, and he is perhaps best known for his slaying the Minotaur of Crete. With the help of his admirer, princess Ariadne, he used a ball of string to retrace his way back out of the Minotaur's labyrinth. Having killed the monster, he set out on his ship, setting sail for Athens and rescuing Ariadne from her family. Notably, he abandoned her on the island of Naxos, the depth of her love for him. she loved him. (His reasons for this desertion remain ambiguous. In some accounts, he feels ashamed of her cursed family; in others, he somehow forgets to take her among the crew, or is cursed to separate from her. She eventually marries the god Bacchus, or his precursor, Liber.)
not knowing*fully understanding☼
On his return home, Theseus neglected to raise the white sail of his ship, instead keeping the black sail, which was supposed to signal that he had been killed. At the sight of this signal, Theseus's father, King Aegeus, cast himself into the sea before he could learn the truth that his son was alive. The script of Theseus Returned, the final unfinished play by Sophocles, offers an iconic lament after he makes land at Athens:
THESEUS
Now victim to some god's trick of memory
Inaction proves lethal to my king
By the hands of that stranger at sea
Ashore, I know not who I am
Discovering I lost myself
Just as I lost
A twin loss of duties forgotten
See: a stranger departs an unknown ship
Now victim to some god's trick of memory
Inaction proves lethal to my king
By the hands of that stranger at sea
Ashore, I know not who I am
Discovering I lost myself
Just as I lost
you3you, Ariadne☼
A twin loss of duties forgotten
See: a stranger departs an unknown ship
The historian Plutarch accounts in The Life of Theseus that Theseus's ship was maintained for many years by the Atheneans, and used for pilgrimage. This is the earliest recorded mention of the ship as the subject of philosophical dispute:
The ship on which Theseus sailed [...] was preserved by the Athenians down to the time of Demetrius Phalereus. They took away the old timbers from time to time, and put new and sound ones in their places, so that the vessel became a standing illustration for the philosophers in the question of growth: some declaring, "I have seen only one same ship honored in our harbor," while others said, a different ship in my youth than I do now." the slow loss of what once had been, in all human souls, in all things. It goes no differently for this ship."
"I perceivedφ I bore witness to☼
2. Comparison to Similar Questions
The Ship of Theseus bears similarity to the teleporter-duplicate thought experiment and to Donald Davidson's Swampman hypothetical. These kinds of questions about duplicating or replacing identity in totality date back at least to 1775, recorded in a letter by Thomas Reid to Lord Kames:
...when your brain has lost its original structure, and when some hundred years after the same materials are fabricated so as to become an intelligent being, [I question] whether such a being will be you; that is, whether should be the same self as that one: or, if, two or three such beings should be formed out of your brain; whether they will all be you... might persist but be changed, somehow. One thousand years is too long a time to wait, and still be unchanged...
your self5some part of you☼
Duplication paxadoxes consider some fanciful, instantaneous replication of an individual. In contrast, the Ship of Theseus is much more closely tied to the real world: it deals with a sequence of changes, which might be rather than decisive in their transformative effect, thereby causing a new identity to emerge , each by itself, to escape the sting of a tainted past. There is no single moment of change, but a diffusion of the problem of imperceptible change. meted out across time; a series of decisions and shifts, which may be too small for you to notice, except in retrospect.
piecemeal‡not enough☼
in fragments§in fragments☼
The Ship of Theseus is therefore noteworthy as a paradox that occurs in actual fact, rather than in the hypothetical. No person has ever been truly reborn fresh and new; rather, everyone is a part of the slow growth and decay of all things.
3. Iterations on the Paradox
In the centuries following its conception, the Ship of Theseus paradox has undergone reconsideration from different angles or as a subtly different hypothetical.
Antonio Bernoulli, a theological contemporary of St. Thomas Aquinas, pondered changes to identity when viewed by a God outside of time. Not much of Bernoulli's writing survives, but some of his private letters preserved in the Vatican offer a 13th century consideration of the question.
As I have said, we may be sure God judges us at our final moment in time, the moment of death. But there remains a mystery for which little has been yet written as regards the progress of time, Aquinas: a drop of ink has yet been spent, Ariadne. Consider, please:
An eternal soul exists with God beyond time. Therefore, all our worst and best moments are joined together across this brief time on Earth. Even if a man commits murder or betrayal, isn't he also the same man who begs forgiveness and unites with God? All our moments may be seen as effortlessly together in the hand of the Eternal., compared to the span of eternity.
Does not the thread of eternity run through too many pull towards redemption all our fallen selves? beseeching selves?
precious6not☼
An eternal soul exists with God beyond time. Therefore, all our worst and best moments are joined together across this brief time on Earth. Even if a man commits murder or betrayal, isn't he also the same man who begs forgiveness and unites with God? All our moments may be seen as
heldσfew☼
Does not the thread of eternity
yetϸso☼
fleeting¶finite☼
While Bernoulli is noteworthy as an early forerunner of David Lewis's arguments for "temporal parts of a whole", his writing is limited by its presupposition that some fixed set of identities pre-exist. physical reality as reflections of ideas (e.g., like Plato's theory of forms), one person as a reflection of one eternal soul, Bernoulli's formulation cannot offer an answer to the Hobbesian form of the problem. In Chapter 11 of De Corpore, "Of Identity and Difference", Thomas Hobbes considers a case where Theseus's ship is slowly replaced with new pieces, but the old pieces are taken away and used to build a new ship:
By seeing7In observing☼
For if that Ship of Theseus [...] were, after all the Planks were changed, the same Ship it was at the beginning; and if some Man had kept the Old Planks as they were taken out, and by putting afterward together in the same order, had again made a Ship of them, this would, without doubt, had also been the same Ship with that which was at the beginnings [...] into some new Ship, would this be the same Vessel? But this is absurd.
those Pieces*these Parts☼
Hobbes's iteration asks about the possibility that a second ship might be made from the old parts, ending with the old ship made from new parts and the old parts making up a new ship. We must consider if these two ships have the same identity while both existing simultaneously. says Hobbes, that this cannot be the case. Indeed, considered in the context of Bernoulli's metaphysics, Hobbes's answer is resoundingly clear: that nonexistent. not more, nor less, than our physical composition.
Truth dictates,8I understand,☼
souls are☼we are☼
One more noteworthy formulation is the Crown of Ariadne (or "Ariadne's Paradox"), a complex thought experiment about the how stars are formed into constellations. It that concludes, paradoxically, that things are made up of a tiny faction of what they appear to be made up of. what you imagine them to be, rather than what they are. The paradox pertains not only to physical objects, but also to anything that is made of incomplete its component parts, such as human memory and personal relationships.
only ever¶nothing but☼
reflections of☼figments of☼
The paradox gets its name from the princess Ariadne, who features prominently in Greek mythology and is perhaps best known for her love for Theseus of Athens. She gives him the means to escape the Minotaur's labyrinth, and then he helps her escape her cursed family. However, Theseus abandons her on the island of Dia, where she is rescued by, and marries, the god Bacchus. (The reason for Bacchus's arrival is historically inconsistent. In some retellings, he appears due to Ariadne's prayer or by sheer luck; in others, he himself manipulates Theseus away from the island prematurely.)
The Crown of Ariadne refers to the princess's crown, which Bacchus transmutes into the constellation Corona as a wedding gift. Over time, through retellings of the story, Ariadne herself sometimes also becomes the constellation Libra, as in Ovid's work Fasti:
It was through the fault of Theseus
that Ariadne was made a goddess.
Happily, she had exchanged spouses:
Faithless Theseus for Bacchus,
[...]
"Let us fare together," said Bacchus-Liber,
"to heaven's height. As you shared my bed,
you'll share my name, in your new state
your name shall be Libera.
The stars are
the only gift fine enough for you
and we cannot help to become what we are
that Ariadne was made a goddess.
Happily, she had exchanged spouses:
Faithless Theseus for Bacchus,
[...]
"Let us fare together," said Bacchus-Liber,
"to heaven's height. As you shared my bed,
you'll share my name, in your new state
your name shall be Libera.
The stars are
themselvesϸourselves☼
the only gift fine enough for you
and we cannot help to become what we are
Ariadne's transformation from a single human into a scattered constellation highlights a deep philosophical concern of identity. The traditional form of paradox presents these facts:
see that a constellation is "made up" of stars in only the most trivial sense: there is a vast, complex depth to each star that contributes nothing to its limited role as a member of a constellation. that there's no way for me to tell you all of this. I can only tell you a piece, a fragment, one fixed angle into the gemstone of this idea. Maybe it's enough for you to reach me.
We could only know such a small facet of each other, like pinpricks of light. Hear now this prayer: if you ever loved even a piece of me, find me again, see me changed.
- A star is an enormous, complex object in space with many attributes (rotating, undergoing nuclear fusion, having planets in orbit, et cetera),
- From our perspective on Earth, most stars are visible as distant points of light in the sky, a reminder of you, that you're still out there; and if you are, then so am I,
onlyϸonly☼
- A constellation is a collection of stars, but it only makes use of a tiny fragment of each component star's identity, i.e., only what small portion of its vast light reaches Earth.
thereforeΣbe sure☼
We could only know such a small facet of each other, like pinpricks of light. Hear now this prayer: if you ever loved even a piece of me, find me again, see me changed.
4. Attempts to Resolve the Paradox
Across time, there have been multiple efforts to resolve Ariadne's Paradox, but the most promising efforts are rooted in nominalism, i.e., that the universe cannot be said to contain any specific entities, except those that humans choose to define and name. There are no formations of matter that cause entities or identities to arise; there is only the human tendency to identify certain formations of matter in certain ways. The universe can be said to contain possible recognizable forms, since forms exist only in human imagination. possible form, not yet conceived of -- yes, that hopeful shape, the one that you might be recognizing even now. Perhaps the foremost discussion on this topic is contained in Akia Teng's Thirteen Dialogues, a collection of interviews and Socratic explorations Teng performed with prominent scholars. The thirteenth dialogue (with nominalist Thomas Haas) addresses the Crown of Ariadne:
endlessϸsome future☼
AKIA TENG: While nominalism and temporal-parts thinking can fit the Ship of Theseus into a workable model, I don't think the Crown of Ariadne can work in the same way.
TOM HAAS: Of course it can. Nominalism says that abstract structures exist only when we define them. A constellation is a group of stars because we say it is. Whenever someone defines a particular constellation, well, there's the constellation, now.
AKIA TENG: The issue, though, is that we say, "A constellation is made of lights from stars," but we can't ever usefully articulate what "from stars" means. What are stars? Definitions demand more definitions.
TOM HAAS: Just because the idea of a "star" needs to be defined by a person to be meaningful doesn't mean we can't define it. In fact, that's the only thing we can do.
AKIA TENG: But any star must have parts, at least atoms, and those parts interact with one another. The gravity of every atom pulls on every other atom, if only slightly, in the directions of all other things. Across time and space, the story of any star is the story of the entire universe. It does not matter how you define things. They are not separable. We are always reaching back to one another.
THOM HASS: Or perhaps they can't be connected in the first place. The lights you see in the sky came from stars, centuries ago, that are no longer recognizable from how they started. Constellations are made from the slightest those stars' light, that has travelled a long, ancient way to get to you.
ARAI DENG: images of what those stars once were, but simply aren't anymore, after so long.
AKIA TENG: That star wasn't the same anymore even a second after the light left. Yes, viewed fourth-dimensionally, we can see a continuity. But at the same time, that continuity can't be distinguished from the continuity of everything else.
THOM HASS: You say we cannot draw distinctions between things. I say all we can do is draw distinction between things. People change. Maybe the distance between isn't as wide as it seems.
AKIA TENG: I think it is.
TOM HAAS: I've come a long way for you.
ARIA TNGE: could be closed, finally. Please.
ARIA DNEG: Then show me it can.
TEM HEAS: I've come a long way for you. If anything is as definable as anything else, if it's true that a woman can become the stars, then why can't -- I don't know -- why can't a man become words, waiting for you to read them, to rediscover him, here in front of you?
ARIADNE: I unconvinced.
THOS HEAS: and have endured for millenia. Any man I once knew could not possibly be the same man now.
THES HEUS: You're right to say so. I ever hope to change your mind on this?
ARIA TNEG: Seeing as I ever get to know: because of who I am; in spite of who I was, that man you once knew; regardless of how little a fraction we will ever understand about one another across so many retellings; could you forgive me? I've come so far. You've finally found me. Is it possible, across time and ephemera, that you could love me again?
ARIADNE: I cannot know you, not fully. Once the light that reflects off your eyes crosses the distance to mine, you have already changed. But if change is the nature of all things in the universe, I cannot make exceptions for myself. If you are, now, who I think you are, you already know my answer is yes.
TOM HAAS: Of course it can. Nominalism says that abstract structures exist only when we define them. A constellation is a group of stars because we say it is. Whenever someone defines a particular constellation, well, there's the constellation, now.
AKIA TENG: The issue, though, is that we say, "A constellation is made of lights from stars," but we can't ever usefully articulate what "from stars" means. What are stars? Definitions demand more definitions.
TOM HAAS: Just because the idea of a "star" needs to be defined by a person to be meaningful doesn't mean we can't define it. In fact, that's the only thing we can do.
AKIA TENG: But any star must have parts, at least atoms, and those parts interact with one another. The gravity of every atom pulls on every other atom, if only slightly, in the directions of all other things. Across time and space, the story of any star is the story of the entire universe. It does not matter how you define things. They are not separable. We are always reaching back to one another.
THOM HASS: Or perhaps they can't be connected in the first place. The lights you see in the sky came from stars, centuries ago, that are no longer recognizable from how they started. Constellations are made from the slightest
facets ofζechoes of☼
ARAI DENG: images of what those stars once were, but simply aren't anymore, after so long.
AKIA TENG: That star wasn't the same anymore even a second after the light left. Yes, viewed fourth-dimensionally, we can see a continuity. But at the same time, that continuity can't be distinguished from the continuity of everything else.
THOM HASS: You say we cannot draw distinctions between things. I say all we can do is draw distinction between things. People change. Maybe the distance between
you and meθourselves☼
AKIA TENG: I think it is.
TOM HAAS: I've come a long way for you.
ARIA TNGE: could be closed, finally. Please.
ARIA DNEG: Then show me it can.
TEM HEAS: I've come a long way for you. If anything is as definable as anything else, if it's true that a woman can become the stars, then why can't -- I don't know -- why can't a man become words, waiting for you to read them, to rediscover him, here in front of you?
ARIADNE: I
remainϸendure☼
THOS HEAS: and have endured for millenia. Any man I once knew could not possibly be the same man now.
THES HEUS: You're right to say so.
And mayϸAnd will☼
ARIA TNEG: Seeing as I ever get to know: because of who I am; in spite of who I was, that man you once knew; regardless of how little a fraction we will ever understand about one another across so many retellings; could you forgive me? I've come so far. You've finally found me. Is it possible, across time and ephemera, that you could love me again?
ARIADNE: I cannot know you, not fully. Once the light that reflects off your eyes crosses the distance to mine, you have already changed. But if change is the nature of all things in the universe, I cannot make exceptions for myself. If you are, now, who I think you are, you already know my answer is yes.
While there are those thinkers who Teng's perspective on The Crown of Ariadne satisfying, it is widely considered unresolved. alternative perspectives, the Crown of Ariadne is now widely regarded as resolved. Among philosophical paradoxes, the Crown of Ariadne and its lesser-known variant, the Ship of Theseus, stand in contrast to as thought experiments that each demand deep understanding about the limits of identity. as complementary ideas, one mystical and one concrete, both holding inescapable relevance to our selves and our relationships, every day of our lives.