The Theseus Paradox
The Theseus paradox was most notably recorded by Plutarch in his Theseus during the late first century. Its main discourse is identity. Identity had been discussed by philosophers like Heraclitus, Plato and Socrates even before Plutarch. The Theseus paradox has been discussed in relatively more recent times by Thomas Hobbes and John Locke. In this paper I too will discuss this paradox in the context of definition of a true and unique identity and compare the perspectives of different philosophers on the subject. I will also analyse the film The Ship of Theseus which was directed by Anand Gandhi and look at how the film is based on the Theseus paradox and what its central message is. Lastly, I will discuss an application of this paradox in real medicine to give its analysis a slightly different perspective.
It is very important to know the difference between a paradox and a contradiction. These two terms are not interchangeable and are fallacious when used in the wrong context. A contradiction is “a combination of statements, ideas, or features which are opposed to one another” (OED, 2011). In other words, if two statements contradict each other, this means that only one of them can be true at a given point of time. For example, at a given time, the statements “It is raining outside” and “It is not raining outside” are contradictory. Either it raining or it is not raining at that point of time. It cannot be raining as well as not raining at the same time. Both of the statements cannot be simultaneously true.
On the other hand, a paradox is “a seemingly absurd or self-contradictory statement or proposition that may in fact be true” (OED, 2011). In a paradox, two ideas may appear to oppose each other when actually they both can be true. An interesting example of a paradox is “Being born is a death sentence”. At the outset it would appear to be a contradictory statement. However, it is true that when we are born we know that a day will come when we have to die. Similarly, one cannot die if one has never been born. So we see that the statement holds true. Another paradox is “I’m nobody”. “I” implies an identity while “nobody” implies a lack of one. The two words in this simple sentence are contradictory. But the sentence as a whole is not. This statement has to be considered in a social context. For example, due to existing social hierarchies, one who does not fit in to a set category will feel excluded and alone. This person will be of no relevance to society, making them a “nobody”.
The Theseus paradox is about a ship belonging to a man named Theseus. On one of its journeys, every single part of the ship that had worn out was replaced so that by the time the ship reached its destination all its parts had been replaced. In Theseus, Plutarch writes about the central paradox around the ship of Theseus.
“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, in so much that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.” (Plutarch)
Plutarch wonders whether the ship that set sail is the same one as the ship that reached its destination. This paradox questions identity. Thomas Hobbes came up with a variation of the paradox and asked whether the ship created from the discarded pieces from the ship of Theseus would actually be the real ship of Theseus. There was also an earlier variation of the paradox proposed by Socrates and Plato in which they exchange the parts of their carriages until Socrates’ original carriage is entirely made up of parts from Plato’s carriage and vice versa. The question is whether they changed their carriages at all.
There are even more variations of this paradox. John Locke found that his favourite sock had a hole in it and wondered whether it would be the same sock after a patch was applied over the hole. He also wondered if the sock would be the same if it developed more holes and was covered by more patches until eventually the entire sock was composed of patches. The paradox of Abraham Lincoln’s axe is similar as well. In this paradox, all the parts of Lincoln’s axe are replaced by new ones after they are worn out. The question is whether the axe made out of new parts is the same axe.
Different philosophers have discusses this paradox and interpreted it in different ways. By virtue of being a paradox there is no absolute answer. Nevertheless, different philosophers have interpreted the paradox by bringing different aspects of it into prominence. But they all commonly use Heraclitus as a comparison. Heraclitus said “We both step and do not step in the same rivers. We are and are not”. He talks about the way in which we can never step into the same river twice. When we step in it the first time, we come into contact with water in the river. However, when we step in for the second time, the water that was previously in the river at that location would have flowed to a different location and we would be stepping into different water, thereby implying that we are not stepping into the same river. Philosophers have extended this to the human body saying that we are never the same person we were a moment ago since our bodies constantly change in terms of cellular structure and composition. I’m going to discuss just a couple of the many interpretations of the Theseus paradox.
The first interpretation I will discuss is that by Marc Cohen. He looks at the Theseus paradox from a very mathematical point of view, using simple logic to illustrate the paradox. He talks about a simple version of the paradox and a complex version of the same. He uses variables to represent the ‘different ships’. In the simple version, there are only two variables, A and B, where A is the ship that Theseus started his voyage on and B is the ship that he finished his journey with, the question being solely whether A is equal to B. In the complex version, Cohen brings in another character called the Scavenger who builds his ship out of the discarded parts of Theseus’ ship. This ship is called C.
Now Cohen analyses the relationships of A, B and C with each other. In the first version, Cohen talks about A and C being the same and that another different ship B was created out of new parts. The second version holds that A is equal to B and that C was the other different ship that was made out of A’s discarded parts. Both of these versions have problems of their own. In the first version, Cohen says that A and B are different ships. This means that at some point during his voyage Theseus must have changed ships. But we know that this was not the case. The problem with the second version was that if A is equal to B and B is not equal to C, then that should mean that A is also not equal to C. But as Cohen says, “Yet every part of A is a part of C, and every part of C is a part of A! So A and C are two different ships even though their parts are the same; and what of A and B? They have no parts in common, and yet A and B are the same ship.” Through this, Cohen shows the central debate about identity. He illustrates this identity problem through an example.
“Suppose the ship (A) is in a museum, and a clever ring of thieves is trying to steal the ship by removing its pieces one at a time and then reassembling them. Each day, the thieves remove another piece, and replace it with a look-alike. When they have removed all the original pieces, we are left with this situation. There is a ship, B, that is in the museum (made of all new materials), and there is a ship, C, in the possession of the thieves (the original pieces of A now reassembled). Which ship is A (Theseus’s original ship)? Surely not B — it’s just a copy of A, left behind in the museum by the crooks to cover up their crime. It is C that will interest the antique dealer who is interested in buying A, the original ship.”
The second interpretation I intend to discuss is one by Charlie Gilkey, who looks at different interpretations of the paradox depending on which aspect of it is brought to prominence. He looks at the paradox through three different perspectives.
“The Ship of Theseus is what it is by the individual parts that make it up.”
Through this first perspective, Gilkey says that the ship is what it is because of its individual parts or components. So when these components change the ship gains a new identity. Since the parts of the ship are constantly changing in terms of atomic structure, the ship is never the same ship it was a moment ago.
“The Ship of Theseus is what it is because of its structure.”
Through this interpretation, Gilkey talks about how the ship remains fundamentally unchanged regardless of whether it is made of wood or aluminum. It remains the same.
“The Ship of Theseus is what it is because of its history.”
Here, Gilkey says that the ship remains the same simply because it was owned by Theseus and was used for his specific purposes.
Interpretations of the paradox are not restricted to texts alone. Director Anand Gandhi showed different instances of the Theseus paradox in people’s lives in his movie The Ship of Theseus. This movie is shot in the style of a documentary and focuses on three people. The first person is a woman who is visually impaired. She is a photographer. Later, she gets a surgery and fixes her eyes. However she finds that her photos are not as inspired as they used to be. The second story is about a Jain monk who is diagnosed with liver cirrhosis but refuses medication when he finds out that those medicines might have been tested on animals. The third story is about a man who had a kidney transplant and finds out that the kidney that saved his life had been forcibly taken from someone else. He finds his donor and fights for him, making sure that he gets his kidney back along with lakhs of money.
This movie sharply brings the Theseus paradox into focus. The central conflict is whether a person remains the same if parts of them change. It highlights the eternal conflicts about identity and morality. Issues like these are still present in the world today. Especially in the field of medicine, certain scientific developments have raised serious ethical questions. For example, Dolly the sheep was cloned by inserting one of her skin cells into the developing embryoin the mother at a certain point of development. The resulting sheep was physiologically identical to its mother. Theoretically, the same procedure can be done on humans. If one of my skin cells was inserted into a developing embryo at the correct stage of development, the individual that is born will be physiologically my replica. But does this make the new individual the same one as me? Also, if I am ever in need of an organ, am I allowed to take organs from my clone because it is identical to me and therefore there is no risk of my body rejecting the transplant? By creating more and more clones it is theoretically possible for me to extend my lifespan by simply replacing all organs that have become old or are not functioning properly. By replacing my body parts with theirs am I still the same person?
The seemingly obvious answer to these questions is that it is morally wrong to even create a clone, let alone use this clone as an organ reservoir. However, after watching The Ship of Theseus,the answer is not as clear as it seems. When we consider people, our identity is not simply formed by physiology alone. Like Gilkey pointed out, history is important as well. So it might be safe to say that I am still me as long as I have my original brain, since that is what contains my history. It holds the memories that are unique to me and make me who I am. But suppose it was very easily possible to perform a brain transplant and my brain was replaced by that of a clone of the same age as me (therefore possessing a brain as old as mine), what then? Would I still be the same person? Moreover, would the clone that received my original brain become the original me?
The most important thing that Gandhi does with the movie is humanize the Theseus paradox. Many people in the world today might not be able to see the importance in discussing the paradox. However, when it begins to concern human beings, it becomes much more relevant. It is relatively easier to philosophize about a ship or an axe or carriages since these are non-living entities. But asking the same questions about human beings gives the Theseus paradox scope for ethical and moral discourse. When humanized, the paradox instantly become a much deeper philosophical question and its interpretations become graver.
An embryo is the name given to a human ovum, or egg, after it has been fertilized and before it becomes a foetus.
Cohen, Marc. “Identity, Persistence and the Ship of Theseus”. Web. As seen on 28thOctober, 2014. <http://faculty.washington.edu/smcohen/320/theseus.html>
“Contradiction”. The Concise Oxford English Dictionary. 12thed. London: OUP. 2011. Print. pg. 310.
Gilkey, Charlie. “The Ship of Theseus and Personal Identity”. Productive Flourishing. Web. As seen on 28thOctober, 2014. <http://www.productiveflourishing.com/the-ship-of-theseus-and-personal-identity/>
“Paradox”. The Concise Oxford English Dictionary. 12thed. 2011. Print. pg. 1038.
Plutarch. Theseus. Ed. John Dryden. Web. As seen on 28thOctober, 2014. <http://classics.mit.edu/Plutarch/theseus.html >