Ship of Theseus

Since ancient Greece, there has been a fierce debate in the philosophical arena about the nature of change and how it affects the identity of objects. Some philosophers believe that nothing ever truly changes and others such as Heraclitus (535-475 BCE), believed that all objects identities are always changing. There are many properties to an object, and many wonder how many properties can change before the object is considered to be something else. This enigma is usually illustrated by the classical story of the ship of Theseus. Change and identity becomes complex and the definition of objects change. An object is a thing that exists in time and space and has many properties or aspects such as size and colour. As these properties change, so do the object and the object’s identity, so therefore objects are always changing with time.

The story of the ship of Theseus has had philosophers puzzled for centuries. The classical story is told by Plutarch (46-120 AD), ‘The ship wherein Theseus and the youth of Athens returned from Crete had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place’, insomuch that this ship became a standing example among the philosophers, for the logical question; one side holding that the ship remained the same, and the other contending that it was not the same ship. Plutarch questions whether the ship would remain the same if each piece were replaced one by one, as the change was only slight. Another puzzle was introduced by philosopher Thomas Hobbes (1588-1679) wondering what would happen if the parts that were replaced were then used to rebuild a second ship. Which ship is the original ship of Theseus? There are two ships, one has been renovated and the other reassembled.

The renovated ship was the original ship of Theseus, but only before it was renovated, all the parts have been replaced which makes it a different ship. Gradually it became a ship that was no longer in its original condition but held onto the legend of Theseus. The ship seized to be his ship from the first part that was replaced. Once the last piece of wood was replaced with a new one, it was a complete new ship. The reassembled ship on the other hand, has all of the original parts. The ship was Thesues’ original ship and then pulled apart to be planks of wood in a shed. These planks of wood have been separated from each other and so they exist to be individual planks of wood. When put back together, even if every plank of wood is put back in its original spot, it cannot be called the ship of Theseus as the ship was built centuries before and when rebuilt, cannot possibly be the same. Neither ship can possibly be the ship of Theseus.

Whichever way we look at this puzzle, there will be a contradiction. The renovated ship holds the legend of Theseus and the reassembled ship has all the original parts. The process of dismantling and reassembling usually preserves identity and so does part replacement. But with the two ships, the processes produce conflicting results. The renovated ship is Theseus’ ship according to one set of criteria, and the reassembled ship is also Theseus’ ship according to another set of criteria. This raises the question of how many times can an object be pulled apart and put back together, and still remain the same. Objects properties can change with time, or with dismantling and reassembling. When a new object is created out of parts from another object, those parts have lost their identity as a whole because they are no longer together, and they form a new identity with the new parts. If two objects are the same in every property, then they are identical. Both ships are not identical even though they may look the same, the reassembled ship has the old original parts and the renovated ship has new parts that were manufactured centuries later. Our common sense intuition tells us that two objects cannot exist in the same place at the same time and that there cannot be two objects that hold the same identity.

The concept of identity, simple and settled though it may seem, gives rise to a great deal of philosophical perplexity. These are presented in the form of paradoxes — arguments from apparently undeniable premises to obviously unacceptable conclusions (Deutsch H, 2008). How we answer questions on identity will depend on what thing we are considering. We have a natural assumption that composite objects can change its qualities over time, and it is safe to say that one and the same thing can change its parts over time. Yet with the story of the ship of Theseus, this threatens the ordinary ways of talking about this matter. Perhaps the conclusion could be that identity is not what matters. What matters instead is some other relation, but one that accounts as easily as identity for such facts that the owner of the restored ship would be entitled to the reassembled ship for the case of personal identity. But this also creates conflict on the claim of identity, as there are two objects that cannot share one identity. ‘A thing is an intactly persisting temporal object if it exists during a period of time and is such that, at any other moment of its existence, it has the same parts it had at any other moment of its existence’ (Jubien M, 1997).

Metaphysics is a branch of philosophy that deals with the first principles of things, including abstract concepts such as being, knowing, identity, time and space (Oxford 2011). Metaphysics goes back to Aristotelian philosophy; Aristotle (384–322 BC) credited earlier philosophers with dealing with metaphysical questions. A Metaphysician attempts to explain the fundamental notions by which people understand the world and its existence. The study looks closely at objects and their properties, space and time, cause and effect and possibility. Ontology is the main branch of metaphysics as it investigates the main categories of being and how they relate to each other. A common discussion found in metaphysics is that things can be qualitatively identical, by sharing some properties. They can also be numerically identical by being one. The two different ships that look identical would be qualitatively, but not numerically identical. A ship can be numerically identical only to itself. Many philosophers have different solutions to the questions of identity and existence. Heraclitus (535-475 BCE), believed that things are always changing.

He is best known for his doctrines that things are constantly in universal flux and that fire is the basic material of the world. Plato’s own statement on Heraclitus: ‘Heraclitus, I believe, says that all things pass and nothing stays, and comparing existing things to the flow of a river, he says you could not step twice into the same river’ (Graham W, 2011). Reverting to Theseus’ ship, if using the concept that things are always changing, then neither of the ships are Theseus’ ship. If this interpretation is right, this means we cannot encounter something twice, or is it that some things stay the same only by changing. Things or objects stay the same but change over time. This theory seems confusing. Heraclitus explains just how contraries are connected: ‘as the same thing in us are living and dead, waking and sleeping, young and old. For these things having changed around are those, and those in turn having changed around are these’ (Graham W, 2011). In philosophy, idealism is also a metaphysical theory about the nature of reality. According to metaphysical idealism, the external world consists of ideas, which being ideas can only exist in the mind.

According to this view, reality is thus mental or spiritual. The opposing philosophical view is called materialism. Materialists maintain that reality consists of physical objects alone and that it is governed by purely physical forces (The World Book 1996). George Berkeley (1685-1753) was a great philosopher in the early 1700’s. He was a metaphysician that was famous for defending idealism, which is that reality consists only of minds their ideas. Berkeley’s argument is that we perceive ordinary objects and we perceive only ideas, so therefore ordinary objects are ideas. Berkeley claimed that he did not deny that the physical world exists, his idealism theory is about the nature of the physical world, not its existence. Most metaphysicians would agree that we could only know the world in the form it appears to us. The world appears to us depending on our minds, senses, emotions and traditions. The most obvious objection to idealism is that it makes things that exist and imaginary things the same. According to this method nothing is actually real, and even if it is, we cannot tell the difference. If we apply this to the ship of Theseus, both ships identities rely on our minds, which seems obscured.

If we apply this to any object, no object will have identity. When philosophers want to understand the nature of the universe, they often begin to examine space and time. Is it possible for there to be time without change? Some metaphysicians believe that space and time are absolute. Space and time, along with what they contain, are not things or properties of things, but they belong to the appearance of things. Solipsists have the view or theory that the self is all that can be known to exist (Oxford 2011). As to space itself, Solipsists state that the world is illusionary, that it does not exist or at least not as perceived. So everything we see, touch and feel is all an illusion of the mind. Solipsism is opposed to all forms idealism and realism, as they claim there is something outside the idealist’s mind, which is another mind. This theory seems bizarre, as the mind should be inside the skull and not floating. There is no explanation as to where the other mind would be located, if floating next to the mind or not and if this second mind is only relevant to idealists. In my opinion, objects and their properties change with time. In regards to the ship of Theseus, Theseus no longer has a ship.

Although the renovated ship may hold the legend of Theseus, it technically is not his ship. The parts that make up the ship are not original. The ship may look identical to the original, but when an object changes its properties, it is no longer the same object. The reassembled ship also could not be Theseus’ ship. Even though the parts are original, they are not in the original condition. When an object is pulled apart and then put back together, it is a different object even if it is identical to the object it originally was. An object and its properties can only remain the same if nothing changes. Even if centuries pass, if the object has its original properties then it is the same. The identity of an object is broken when it is pulled apart and the properties form new identities as a new object. In this discussion I believe that there is no right or wrong opinion or answer in relation to the ship of Theseus. There are so many ways to look at this puzzle and there can be many conclusions, all as valid as each other.

References

1. Deutsch, H December 21st 2008, “Relative Identity”, The Stanford Encyclopedia of Philosophy, viewed 12th September 2011, <http://plato.stanford.edu/entries/identity-relative/#2>. 2. Graham, W June 21st 2011, “Heraclitus”, The Stanford Encyclopedia of Philosophy, viewed 10th September 2011, <http://plato.stanford.edu/archives/sum2011/entries/heraclitus/>. 3. Jubien, M 1997, Contemporary Metaphysics, Identity through time, Blackwell Publishers USA, pp 25-29. 4. Oxford Dictionaries, 2011, Oxford Dictionaries webpage, viewed 12th September 2011, < http://oxforddictionaries.com/> 5. The World Book Encyclopedia 1996, vol 10,13,15, ed. Groman J, World Book Inc. Chicago, USA.