The Ship of Theseus

ABSTRACT: Endurantism and perdurantism are theories that describe how objects can persist through time. These theories will be used in an effort to solve a puzzle that has been dated all the way back to the first century: the Ship of Theseus. It will be determined that the two theories fail in solving the Ship of Theseus puzzle. According to Brian Garrett of Australian National University, metaphysics is concerned with the nature and identity of objects. 1 In order to increase understanding of the identity of objects, puzzles of constitution and identity are used by philosophers.

There is a puzzle common in metaphysics: the Ship of Theseus, which was believed to be recorded by Plutarch in the late first century2. It is complex puzzle that consists of three different scenarios. The first scenario depicts a ship being dismantled and then rebuilt. The second scenario portrays the ship being completely remodeled. The third scenario is a mixture of the previous ones that have the ship being completely remodeled, but the removed planks are used to construct another ship. In order to solve this puzzle, one must be able to identify which ship is the Ship of Theseus.

Philosophical theories can be used to solve philosophical puzzles such as this one and there are two theories that exist that help one understand how objects persist through time: endurantism and perdurantism. According to endurantism, ordinary objects are wholly present at each moment of time at which they exist3. In perdurantism, objects are four dimensional entities that consist of temporal and spatial parts and these objects persist by having different temporal parts at different times4. Once one has knowledge of endurantism and perdurantism, the theories can be used to solve puzzles such as the Ship of Theseus.

However, in this paper, it will be shown that the puzzle of the Ship of Theseus cannot be solved using endurantism and perdurantism. This is because attempts made by endurantists and perdurantists result in unintuitive consequences. This will be done first by explaining and assessing endurantism and perdurantism. Then it will be shown that the two theories fail in solving the Ship of Theseus because of problems that are encountered. After that, the Extensionality Principle will be discussed, which is used by perdurantists as a criterion for identity.

It will be determined that this principle is also flawed and is also unable to give an account for the identity of objects. Firstly, endurantism is the view that physical objects are three-dimensional and move through time. They are wholly present at each moment of time at which they exist. For example, if a man was born in 1975, attended kindergarten class in 1980, and graduated from high school in 1993, endurantists would claim that this man was wholly present at each of those different times. He will continue to wholly exist in the future as well.

Primary motivation for this theory is that it is a more conventional view and is more in conjunction with believed upon ideas about the world. For example, when a woman is talking to someone, she believes that she is talking to that person as a complete object, wholly present; as opposed to just a temporal part of an object. The theory of endurantism has been explained. It must be noted, however, that this theory holds that two numerically distinct, but wholly present objects can co-exist for some of the time or at all times.

Brian Garrett says that this hinders the authenticity of endurantism because the statement is strange5. Perdurantism does not have this problem. The theory of perdurantism is the view that ordinary objects are four-dimensional and are composed of temporal parts. An object is not wholly present at every possible time at which it exists because only its temporal parts exist. In the previous example, when the man is born, or attends kindergarten, or graduates from high school, the man is not wholly present according to perdurantism.

Instead, it is the man’s temporal parts that existed during those events; the man itself exists as a four-dimensionally extended whole. Primary motivation for perdurantism is that this theory is able to account for change within a physical object because the objects are four-dimensional. On the contrary, endurantism does not have this luxury. Perdurantism is also primarily motivated by how it better accommodates Albert Einstein’s theory of special relativity. There are problems that arise if both endurantism and special relativity are true. According to Steven D. Hales and Timothy A.

Johnson of Bloomsburg University, “it would be misguided to argue” for endurantism because special relativistic effects “are negligible at human speeds”. 6 The theory of special relativity does not allow for endurantism because of how it requires objects such as humans to move through time at a slower speed than the speed of light. Given that special relativity is a widely accepted theory, perdurantists have strong motivation to prove their view7. Secondly, even though endurantism and perdurantism help explain the persistence of objects over time, neither view is able to solve the puzzle of the Ship of Theseus.

In the Ship of Theseus, there are three different scenarios. In the first scenario, the Ship of Theseus is dismantled and then rebuilt with each plank being returned to its original location— we’ll call this ship Y1. In the second scenario, the ship is completely remodeled with an entirely new set of planks— we’ll call this ship X1. In the third scenario, two ships are involved. The ship from the second scenario (now called ship X) is present, but an entirely different ship that is being constructed out of the planks that had been removed (called ship Y) is also present.

In order to solve this puzzle, the Ship of Theseus must be identified. However, flaws in endurantism are shown by how the endurantist must deny that Y1 is equal to Y. This is done in order to respect the necessity of identity and non-identity which states that if x = y, then necessarily x = y8. However, what this entails is that one could claim that if the removed planks had not been replaced in the third scenario, then ship Y would not have existed and instead ship Y1 would have existed. This means that the existence of ship Y or Y1 entirely depends on whether or not the removed planks were replaced.

Brian Garrett refers to this consequence as “strange” because “we don’t think that the existence of a particular ship (or of anything else in space and time) depends on what happens in a region of the universe which exerts no causal influence on it”9. This is a flaw for the endurantism theory because it denotes that an object’s existence is dependent on an event that has no direct influence on it. Furthermore, perdurantism also fails in correctly solving the Ship of Theseus. According to perdurantism, the third scenario involves the presence of two ships prior to the repair of the Ship of Theseus.

They are overlapping one another. This represents that the ships have a common temporal segment where they are basically one and the same ship. After the repair, the two ships separate with one being ship X and the other being ship Y. The problem, however, is that one cannot think that there are three possible outcomes anymore. One cannot think that the future of the Ship of Theseus will be the same as that of the ship in the first scenario, the ship in the second scenario, or the ships in the third scenario because each of the ships are distinct from one another.

This is a problem, according to Garrett, because people “could sensibly wonder” if the future for the Ship of Theseus will be like any of the three scenarios when it is being constructed10. He means that ordinary people should be able to think about the Ship of Theseus and think about what future it might behold. However, the theory of perdurantism must deny that three possible futures are available for the ship. As a result, we are left with either believing that people are not able to wonder about the ship’s future (which cannot be true) or perdurantism is unable to solve the puzzle of the Ship of Theseus.

Moreover, perdurantism fails in solving the puzzle because of the name: ‘Ship of Theseus’. It has been discussed that the Ship of Theseus has a temporal part where there are two overlapping ships. However, which of the two overlapping ships is the actual Ship of Theseus when the name is being called? This is a problem because both ships cannot be called the Ship of Theseus. Perdurantism cannot account for this confusion. This shows that perdurantism is unable to solve the puzzle of the Ship of Theseus.

Overall, the theories of endurantism and perdurantism have been explained and it has been shown that both theories are unable to solve the puzzle of the Ship of Theseus. However, there are criterions for identity that exist that could provide a criterion of identification for objects through time. One criterion for identity that will be talked about is the Extensionality Principle; it is used by perdurantists because it is a criterion of identity for four-dimensional objects11. The Extensionality Principle, according to Garrett, states: if x and y are objects with the same proper parts, then x=y.

This means that if two different objects have the same properties, then the two objects are the same12. However, there are flaws in the Extensionality Principle that causes it to fail in providing a criterion of identification. According to Lecture notes, in order for objects to be identical, it is not enough for the object to have all the same parts. This is because the parts of identical objects must be related to each other or arranged in a certain order13. Therefore, a problem arises regarding temporal parts of an object. How do the temporal parts have the proper order?

As a result of this problem, the Extensionality Principle must be revised. But if it is revised, according to lecture notes, the principle will no longer be an extensional principle14. Furthermore, there is no explanation as to why time would provide the correct order for temporal parts of an object. These problems show that the Extensionality Principle fails in providing a criterion of identification; and this harkens back to how the puzzle of the Ship of Theseus cannot be solved. It has been shown that the puzzle of the Ship of Theseus cannot be solved.

This was first determined by explaining the theories of endurantism and perdurantism and revealing the primary motivation for each of them. These theories depict how objects persist through time; yet, the theories cannot be used to correctly solve the Ship of Theseus puzzle. Lastly, the Extensionality Principle was described and it was shown that the principle was unable to solve the Ship of Theseus puzzle. As one can see, the Ship of Theseus is a difficult puzzle to solve and it has been around since the late first century. Will there ever be a theory that correctly identifies the Ship of Theseus once and for all?

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The Ship of Theseus. (2016, Aug 24). Retrieved from https://phdessay.com/the-ship-of-theseus/

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