Ship of Theseus

Ship of Theseus
The Ship of Theseus is a thought experiment about whether an object which has had all of its original components replaced remains the same object. According to legend, Theseus, the mythical Greek founder-king of Athens, rescued the children of Athens from King Minos after slaying the minotaur and then escaped onto a ship going to Delos. Each year, the Athenians commemorated this by taking the ship on a pilgrimage to Delos to honor Apollo. A question was raised by ancient philosophers: After several centuries of maintenance, if each individual part of the Ship of Theseus was replaced, one at a time, was it still the same ship?
In contemporary philosophy, this thought experiment has applications to the philosophical study of identity over time, and has inspired a variety of proposed solutions and concepts in contemporary philosophy of mind concerned with the persistence of personal identity.
History
In its original formulation, the "Ship of Theseus" paradox concerns a debate over whether or not a ship that had all of its components replaced one by one would remain the same ship. The account of the problem has been preserved by Plutarch in his Life of Theseus:
Centuries later, the philosopher Thomas Hobbes extended the thought experiment by supposing that a custodian gathered up all of the decayed parts of the ship as they were disposed of and replaced by the Athenians, and used those decaying planks to build a second ship. Hobbes posed the question of which of the two resulting ships, the custodians or the Athenians, was the same ship as the "original" ship.
Hobbes considers the two resulting ships as illustrating two definitions of "Identity" or sameness that are being compared to the original ship, 1) the ship that maintains the same "Form" as the original, that which persists through complete replacement of material and 2) the ship made of the same "Matter", that which stops being 100 per cent the same ship when the first part is replaced.
Proposed resolutions
The Ship of Theseus paradox can be thought of as an example of a puzzle of material constitution — that is, a problem with determining the relationship between an object and the material of which it is made.
Constitution is not identity
According to the Stanford Encyclopedia of Philosophy, the most popular solution is to accept the conclusion that the material out of which the ship is made is not the same object as the ship, but that the two objects simply occupy the same space at the same time.
Temporal parts
Another common theory put forth by David Lewis, is to divide up all objects into three-dimensional time-slices which are temporally distinct, which avoids the issue that the two different ships exist in the same space at one time and a different space at another time by considering the objects to be distinct from each other at all points in time.
Cognitive science
According to other scientists, the thought puzzle arises because of extreme externalism: the assumption that what is true in our minds is true in the world. Chomsky says that this is not an unassailable assumption, from the perspective of the natural sciences, because human intuition is often mistaken. Cognitive science would treat this thought puzzle as the subject of an investigation of the human mind. Studying this human confusion can reveal much about the brain's operation, but little about the nature of the human-independent external world.
Following on from this observation, a significant strand in cognitive science would consider The Ship not as a thing, nor even a collection of objectively existing thing parts, but rather as an organisational structure that has perceptual continuity.
Alternative forms
In Europe, several independent tales and stories feature knives that have had their blades and handles replaced several times but are still used and represent the same knife. France has Jeannot's knife, Spain uses Jeannot's knife as a proverb, though it is referred to simply as "the family knife", and Hungary has "Lajos Kossuth's pocket knife". Several variants or alternative statements of the underlying problem are known, including the grandfather's axe and Trigger's broom, where an old broom or axe has had both its head and its handle replaced, leaving no original components.
In Japan, the Ise Grand Shrine is rebuilt every twenty years with entirely "new wood". The continuity over the centuries is considered spiritual and comes from the source of the wood, which is harvested from an adjoining forest that is considered sacred.
The ancient Buddhist text Da zhidu lun contains a similar philosophical puzzle: a story of a traveler who encountered two demons in the night. As one demon ripped off all parts of the traveler's body one by one, the other demon replaced them with those of a corpse, and the traveler was confused about who he was.
The USS Constitution is acknowledged as a modern Ship of Theseus by the USS Constitution Museum. Since it was first laid down in 1794, the Constitution has undergone numerous repairs, modifications, and reconstructions. "The USS Constitution has essentially none of its original wood but we believe no one would consider it a replica. It is Old Ironsides."
In The Three Basic Facts of Existence, Piyadassi Thera uses the teachings of Dharma to suggest that nothing in the universe is ever the same.
The French critic and essayist, Roland Barthes, refers at least twice to a ship that is entirely rebuilt, in the preface to his Essais Critiques (1971) and later in his Roland Barthes par Roland Barthes (1975); in the latter, the persistence of the form of the ship is seen as a key structuralist principle. He calls this ship the Argo, on which Theseus was said to have sailed with Jason; he may have confused the Argo (referred to in passing in Plutarch's Theseus at 19.4) with the ship that sailed from Crete (Theseus, 23.1).
See also
Boyd Coddington
Brain implant
Bundle theory
Haecceity
Interchangeable parts
Mereological essentialism
Neurath's boat
Perdurantism
Philosophy of self
Przekładaniec
Sorites paradox
Śūnyatā
Swampman
Teletransportation paradox
Transporter (Star Trek)
Notes
References
Further reading
External links
S. Marc Cohen's Lecture notes on "Identity, Persistence, and the Ship of Theseus" from the University of Washington
Eponymous paradoxes
Identity paradoxes
Logic
Identity (philosophy)
Logical paradoxes
Metaphors referring to ships
Theseus
Thought experiments in philosophy
Philosophical paradoxes
Ancient Greek logic