Philip Gregory: Theseus' Ship

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The old philosophical problem of Theseus’ Ship goes something like this: Theseus sets sail on his ship (ship A). This ship carries replacement parts that are identical to the original ship, enough to make a second ship (ship B). As the journey goes on, Theseus gradually replaces pieces of his ship with those replacement parts. At the end of the journey, the ship that floats into the harbor has zero percent original parts (ship A parts) and one hundred percent replacement parts (ship B parts). The question arises: is the ship that arrives in the harbor the same ship? In this essay, I argue that the paradox is fundamentally flawed, and a conceptual and semantic problem, rather than a metaphysical one.

Submitted: December 12, 2013

A A A | A A A

Submitted: December 12, 2013

A A A

A A A


Theseus’ Ship

The old philosophical problem of Theseus’ Ship goes something like this: Theseus sets sail on his ship (ship A). This ship carries replacement parts that are identical to the original ship, enough to make a second ship (ship B). As the journey goes on, Theseus gradually replaces pieces of his ship with those replacement parts. At the end of the journey, the ship that floats into the harbor has zero percent original parts (ship A parts) and one hundred percent replacement parts (ship B parts). The question arises: is the ship that arrives in the harbor the same ship? To complicate things further: what if the ship A parts were tossed over board when they were replaced? What if a scavenger found them and reassembled them into a second ship that was identical to the original? What if this scavenger then sailed to the same harbor and floated up alongside Theseus? Now, which ship would be Theseus’ ship? Would it be the original ship that the scavenger now possesses (ship A) or the renewed ship in which Theseus arrived (ship B)? Several solutions have been offered for this problem, but none come without complications, and this is because the current solutions fundamentally misunderstand the underlying problem. The Theseus “paradox” is not a metaphysical problem, but a conceptual and semantic problem - a product of a discontinuous mind that craves absolutism, and realizing this fact makes a solution easy to attain. Before I discuss that solution, however, a summary of the most common (and insufficient) solutions is needed.

Common Solutions to the Theseus Paradox

One solution to the Theseus problem is to deny that an object goes where its parts goes. This is the idea that, even if a person were to deconstruct a ship and reassemble it with the same parts and in exactly the same way, the resulting assemblage would not be the original ship. In other words, Theseus’ ship is only his ship while all of the original parts are in place. This is not a very acceptable idea to most people, for obvious reasons; most people believe that a ship can survive the replacement of, say, a single board, without it ceasing to be a ship. For this reason, this first solution is easily discarded.

Another solution is to argue that ordinary objects can survive some gradual change, but not complete change. This solution is unacceptable mainly because it rests upon an arbitrary decision. How do we determine at which point Theseus’ ship is still his ship, and at which point it is not? Does the ship remain Theseus’ while it contains ninety percent of the original parts, or fifty percent of the original parts, or twenty percent of the original parts? How many boards must be replaced before Theseus’ ship becomes a different ship? If we asked this question to a classroom of students, there would likely be as many opinions as to what was the correct answer as there were students in the room, because at any time that someone might say, “ah, yes, there, at that point, now it is no longer Theseus’ ship,” we would find that the choice they made was entirely arbitrary. For this reason, the second solution can be discarded.

Another solution is to say that ordinary objects never survive gradual change. This is the view that even one board replacement destroys Theseus’ ship. Not only is this view implausible (who would believe that a single board replacement could destroy a ship) but also it results in the idea that, during Theseus’ journey, we would have as many new ships as we had part replacements. Again, this seems arbitrary, and also counterintuitive. When we replace a flat tire on a vehicle, for example, we do not suddenly claim to have a new vehicle. Objects seem to survive at least some change, and so this solution is rejected.

Yet another solution is to claim that both ship A and ship B are Theseus’ ship, but that A is not equal to B. This view avoids the pitfalls of gradual change, but denies that identity is transient. In this case, we end up with two ships that are both Theseus’ ship, without any real justification that seems plausible. Rather than really addressing the problem at hand, this solution instead seeks philosophical superiority, and it succeeds, in that it avoids the pitfalls of gradual change. As a solution, however, it is little more than a shell game. Rather than solve the paradox, it solves one aspect of the problem, and presents us with a solution that is more counterintuitive than the problem it sought to avoid. Thus, it is rejected, on that grounds that it does not seriously address the fundamental issues at hand.

In the last solution, we are asked to change how we think about ships. We are asked to imagine that ships are not three-dimensional objects, but four-dimensional. By adding the fourth dimension – time – we can now discuss something called time slices. By considering time slices, we are able to argue that there are no whole ships present at the beginning of Theseus’ journey, but, rather, there is one ship that has a ship A part at the beginning of the journey, and a ship A part at the end of the journey, (no replacements) and a second ship that has a ship A part at the beginning of the journey, and a ship B part at the end of the journey (replacements). In this case, there are two ships that have equal claim to being the ship of Theseus. While this solution may seem the best so far, and while it does seem to agree with modern science and General Relativity, this solution has several problems. For one, if we rely on time slices to solve the paradox, we end up with a situation where Theseus’ ship seems more like several distinct objects, rather than one persisting object. There is also the problem of time, since time is relative, and other problems, some of which lead us to the conclusion that the universe is static, and that hard determinism is true. So, although this solution is the most comprehensive, in the end it must be rejected on the grounds that it is unduly complex and unnecessary; it creates far more problems than it solves.

Solving the Paradox

Solving the paradox of Theseus’ ship is far easier than it might at first seem. The aforementioned solutions remain insufficient because they fail to address the fundamental problem of the Theseus scenario. In each case, the solution offered rests upon an assumption: that the Theseus scenario represents a metaphysical problem. Every solution offered (and any solution attempted) that relies upon this assumption is doomed to fail because it does not recognize the Theseus’ paradox for what it is – a conceptual and semantic problem. From an erroneous understanding of cognition, the Theseus paradox gains its strength, but when we consider words and the way they are used, and how concepts are created and implemented, the problem is diffused. To illustrate why, let us consider an argument that makes a similar mistake – one that is diffused in much the same way.

During religious debates, the argument that the laws of logic are immaterial and therefore must be a product of an immaterial mind often arises. The most popular version of this argument is called the TAG argument – the transcendental argument for god’s existence. The problem with this argument is that it relies upon the fallacy of equivocation, and the fallacy of reification. The TAG argument flies in the face of everything we know about cognition. More specifically, it carries the assumption that logical rules exist in the same sense that a car exists, or a tree exists, or animal exists, when in reality, logic is merely a descriptor, a conceptual label - created by humans to describe a particular phenomenon of reality. Take the law of identity. The law of identity states that A=A, and not B – that is, any particular thing has its own unique identity. Proponents of the TAG argument believe that the law of identity, or A=A, exists in the universe – written into the foundations of existence. This conclusion, however, is false. The law of identity is an immaterial concept, and the properties of reality to which it refers are not. By comparing and contrasting any two physical properties of reality we would soon discover what we would conceptually label as the law of identity. There is no unbreakable law that exists, except within our minds. The same is true of all semantic conventions, in all languages and systems of logic, regardless of what label we use. The word blue in Japanese is “ao,” but the thing that both “ao” and “blue” refer to (the color spectrum that humans perceive as “blue”) is what it is, and is not what it isn’t – the label is merely a convention. Similarly, the “laws” of logic and mathematics are also conceptual descriptors. In the same way that proponents of the TAG argument fail to realize that the laws of logic do not “exist” in the way they assume, so do proponents of the Theseus paradox fail to realize that there never was, in any scenario, any ship.

A ship, in a physical sense, is no more a ship than an apple is an apple. Both a ship and an apple are arrangements of particles – atoms, neutrons, and so on. In the case of a ship, the arrangement of wood particles in a particular order is something we have subjectively labeled “ship,” but there is no platonic ship floating about the universe. Identity is not something that exists in the world; identity is a subjective concept that is ascribed to a particular phenomenon that has been interpreted by a mind. Since this is an entirely subjective (and therefore necessarily relative to one property of reality or another) process, it cannot be absolute. The problem with the Theseus paradox is that it begins the scenario with an assumption of absolutes. In the Theseus story, we are presented with a problem that asks, “which of these is a ship,” when we ought to have been asked something like, “which one of these arrangements of matter most closely resembles your subjectively-created concept of a ship?” If we replaced the word “ship” with “abstract concept,” we would quickly find that there is no paradox at all.

If we reject platonic forms and consider the basics of cognition, (the fact that we must infer reality, and ascribe meaning subjectively) the Theseus’ paradox dissolves. A ship is a ship so long as a person decides that it is a ship. In the case of Theseus, whether or not he considered his newly refurbished ship a “new ship” or the “same ship” would depend on whether he had assigned a new conceptual label to the new arrangement of matter, or if he preferred the original conceptual label. Of course, the scavenger might well disagree with Theseus. It is highly plausible that the scavenger might claim that his ship is in fact the ship of Theseus, but, alas, such is the nature of relativity. In life, there are no absolutes, and even if there were, we would never be able to discover them. Even the laws of logic that we consider necessarily true due to the impossibility of the contrary (such as the law of identity, the law of excluded middle, and so on) must be assumed true. Epistemic circularity denies us any way of verifying anything to absolute certainty. This is the nature of cognition: we interpret an assumed fact of reality, and assign that fact of reality a conceptual label. The Theseus paradox ignores this process, and rests upon absolute definitions for words like “ship” and “exist,” while setting up a scenario that clearly illustrates relativity, and thus, the contradiction; thus, the paradox.

It is often difficult to realize that the thoughts inside of our head, no matter how “proven”, no matter how “logical”, simply cannot be absolutely true. We go about saying, “a ship is a ship, not something else other than a ship,” but we fail to realize that the term “ship” is created by our minds, and only useful so long as everyone agrees to the meaning we have ascribed. The Theseus paradox illustrates a situation where reality itself contradicts an erroneous assumption of absolutes. It shows us a situation where even a highly agreed upon definition is called into question. Even the concepts that seem entirely unassailable, says the Theseus paradox, can easily be shown to be relative. In the end, we have only ourselves to blame for being confused by the Theseus paradox. It is our tendency for absolutes and our misunderstanding of cognition that creates the problem. Before any solution to the paradox was ever attempted, we ought to have realized that the paradox itself is flawed, because it rests upon absolute definitions and asks for absolute answers, while discussing relative descriptors and abstract concepts.

Objections

By saying the Theseus paradox is a conceptual and semantic problem rather than a metaphysical one, you are not actually solving the paradox, but merely avoiding it.

It is true that I am dissolving the paradox by suggesting the problem was misunderstood in the first place, but the dissolution is also a solution. Unlike Goodman’s dissolution of Hume’s original problem, my dissolution does not create a secondary problem. By realizing that the Theseus paradox is not a paradox at all, and by understanding the nature of cognition and relativity, we do not arrive at another conundrum, but we arrive at a host of answers – in fact, infinite answers.

If everything is relative, and cognition is as you say, then this leaves us with the conclusion that Theseus’ ship could be his ship and not be his ship at the same time, depending on who was assessing the question. In other words, you have infinite answers, where the other solutions attempted to provide only one answer.

This is true. My solution results in an infinite amount of definitions for what is a “ship”. This is an unfortunate side effect of reality being relative in nature. This may seem unsavory for many, but it is, I believe, the nature of reality – and we can’t argue with reality. There really are an infinite amount of answers to the question, “which ship is this Theseus’ ship?”

You talk about epistemic circularity and the fact that cognition is relative. What evidence do you have for this fact? How does this solve the paradox?

The evidence for epistemic circularity is vast and comprehensive, and I do not have time to present it all here. Suffice to say, neuroscience has provided much hard evidence for epistemic circularity, and so have other scientific fields. We do not actually need this hard evidence, however, to understand our own epistemic circularity. The problem has been known as “the problem of the criterion” for some time in philosophy, and it is, though a perplexing problem, a problem that is very easy to discover. All one must do is ask how one knows something to certainty. If that person is honest, they will be forced to admit that every piece of information that enters their brain is inferred from one property of reality or another, through their senses. The question is: can these senses be trusted? The logical conclusion is that no, we have no way of verifying things objectively by subjective (cognition) means. Our mind is relative to reality, and reality is relative. Concepts, created by the mind, must necessarily follow this pattern. Therefore, the meaning of “ship” is ascribed.

Why wouldn’t philosophers prefer the four-dimension argument (time slices) to your argument?

I cannot say which argument philosophers would prefer, but I feel that the four-dimension argument is a disingenuous one. As explained in my essay, I believe that this argument only seeks to avoid the problem of gradual change, but it does not offer a suitable solution to the paradox. More importantly, it seems to agree with the erroneous conclusion that there can be any one definition for “ship” that is correct, and it misinterprets the paradox as a metaphysical problem, when in fact it is a semantic and conceptual problem.

Your argument relies on the word “concept,” and you say that “ship” is merely a concept. Explain?

“Ship” is an abstract concept. In the case of the Theseus paradox, there never was any ship at all – only the abstract concept for “ship”. Likewise, the planks are not really planks, but an abstract concept we call “plank”. Both the planks and the ship are arrangements of wood particles (“wood” and “particles” also being concepts). So in the end, the problem is not metaphysical. Which ship is the original ship depends upon how you define or accept the abstract concepts “ship” and “original”. In the end, the Theseus paradox is much like the false dichotomy that asks: “is it absolutely true that there is no absolute truth?” No relative answer can be given, without the paradox starting again. The solution then, is to deny the premise of the paradox itself.

Conclusion

I have argued that the Theseus paradox can be dissolved (and solved) by accepting that the paradox is not a metaphysical problem, but a semantic and conceptual problem, and that the paradox is a result of a human tendency to seek absolutism. I have argued that the current solutions to the Theseus paradox are all insufficient, and that they share a common failure, namely, accepting the erroneous assumptions of the paradox itself. I have argued that the mind is subjective and relative to certain properties of reality, and that we ascribe meaning to abstract concepts like “ship,” “original” “identity” and “exist,” that we can not be certain of anything, (even necessary truths) and that the Theseus paradox is fundamentally flawed, since it assumes that a definite definition for “original” and “ship” can exist in a scenario that is clearly relative in nature. What I have not discussed, however, is the cause of this craving for absolutism, which I believe to be the discontinuous mind – a mind that has evolved to separate, categorize and subcategorize, and I shall not do so in this essay. Nevertheless, the Theseus paradox remains dissolved, since it can only be considered a paradox so long as one accepts an erroneous understanding of cognition, semantics, and abstract concepts. 


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