The curious case regarding the concept of identity is rooted in it’s subtle, pervasive, and complex nature. Whenever I speak, or try to convey information about something, whether that be a person, an animal, or an object, I am implying it’s identity through speaking of it, but I am not directly addressing it. I am waving away the concept of identity as something universally understood to the point that it doesn’t require any thought or explanation. I seem to act as if identity exists solely for the purpose of conveying information about the world – but does it? Examining the nature of identity might seem like a fool’s errand, or a quixotic undertaking; but the importance that the concept has in our speech and our day-to-day lives warrants a serious, and likely difficult, discussion regarding exactly what it is. Dismissing the necessity of defining identity while continuing to refer to it, will leave us unable to solve the many problems and puzzles regarding identity; it will lead us into contradictions and, ultimately, an incomplete or seriously flawed understanding of our world. To understand how this can happen, we will examine a series of puzzles relating to identity and how E.J. Lowe responds to them.
With regards to the puzzle of The Ship of Theseus put forward by Thomas Hobbes, Lowe begins with the approach that a ship can change all of it’s parts provided that the change is done in a “gradual and piecemeal fashion”(25). This approach, Lowe thinks, appeals to common sense. The alternate view would be that a ship could only change some proportion of it’s parts while being identical to the ship it was beforehand; however, this raises a few issues. First, the limit on how many parts of the ship could be replaced would seem to be arbitrary. Second, if we allow a change of some proportion of parts while maintaining identity, then we risk contradicting the transitivity of identity. Lowe imagines that we allow “up to 5 percent of a ship’s parts”(26) to be replaced while maintaining the identity of that ship. However, if that ship then undergoes a change of completely different parts, then we might have three ships at three different times that differ in parts by more than 5 percent. And so, our initial limit on the change of parts has led us to a contradiction where the initial ship is identical to the ship after the second reconstruction because of the transitivity of identity, but it is also not identical because the limit is exceeded. So, Lowe thinks that a ship can change all of it’s parts over time because the alternate view that it cannot leads to a contradiction.
This argument regarding the proportion of parts seems to supersede a more pressing matter, that is, the purpose of the parts of The Ship of Theseus. To show where Lowe goes wrong here, I will create a more dramatic example. Imagine that there exists some technology where I would be able to replace any part of my body with another newer part. These new parts are distinct from my old parts in the same way that the new boards on The Ship of Theseus are distinct from the old boards, but they look roughly the same and function the same. Now, by Lowe’s argument, if I am to be able to replace my parts while maintaining my identity, I should be able to replace all of my parts in a “gradual and piecemeal fashion”(25). There seems to be an issue here that is not quite as obvious in the example of The Ship of Theseus. It’s easy to see that if I were to replace my arm, my leg, or the hairs on my head with these new body parts, that I would still be numerically equivalent to who I was before. The only difference is that I have a new arm, leg, or hairs on my head. But does this imply that I could undergo a complete change of parts? There is, as Lowe put it, “hierarchies of composition”(24) involved here. It is not as easy to say, as it is with the case of my arms or my legs, that I would be numerically equivalent with a different brain. That is because when we consider identity, we have to consider the purpose that it serves. It must mean something to be a human being just as it must mean something to be a ship. My identity as a person is not tied to my ability to lift things with my arms, or to run with my legs. Clearly, many human beings live without these abilities. But to be a person is to be an agent and to be an agent is to have the capacity for rational thought and reason as a means of survival. So, the essence of personhood seems to reside somewhere in the brain. To be a distinct person, however, is a different matter from simply being a person. Just as being The Ship of Theseus is distinct from being any other ship. There should then exist something somewhere within my brain that differentiates me from any other person. A first inclination would be the history of thoughts that my brain has had. Past experiences, as the psychologists know, have a serious effect on how the brain thinks, and the unique way that our brains think seems to be what differentiates us from each other.
How does this extend to Theseus’s Ship? In order to discuss the identity of the ship, we ought to understand the purpose of a unique ship and how it is differentiated from any other ship. First, the parts of The Ship of Theseus can be arranged in a hierarchical structure. Just in the same way that my brain has more to do with my identity than the hairs on my head, so too will there be parts of The Ship of Theseus that carry more numerical weight than other parts. A ship is manned by a captain to travel across large bodies of water; it has a wheel, a rudder, a mast, a stem, risings, knees, cappings, and sails. It seems reasonable to say that the mast has more importance to the identity of the ship than the knees. The mast holds the sails which allow the ship to float across the water; the knees, on the other hand, serve to hold the railing which helps the crew from falling off and water from splashing in, but the ship would be a functional ship without it’s knees. In the same way, parts of my brain help me to think in the way that only I do. My knees might help me to walk, but my identity as a person, and as myself, does not depend on my ability to walk.
The planks of the ship are a more challenging matter. Most of the outside of the ship is composed of planks, and they are crucial to the ship’s ability to float. Most of the parts that will be replaced in the puzzle of Theseus’s Ship are planks, but are they necessary for the identity of Theseus’s Ship? My inclination is to say that none of the planks on any wooden ship have any effect on the identity of that ship. My case for the planks is that wooden planks submerged in water are not, or should not be, expected to last as long as the ship. The submerged planks are temporal parts that are important for any ship to float, but not individually notable in any specific ship, such as that of Theseus’s. For clarification, the planks seem to serve the same purpose as the crew on any voyage. Without the crew, the ship will not serve it’s purpose of floating and travelling across the seas; without the crew, it would hardly be a working ship. But the crew is not expected to remain the same on any ship. If The Ship of Theseus embarked on a voyage with set of crew members disjoint from the set of crew members on the previous voyage, we would not say it is a different ship. Such ought to be the case with the planks and any part of the ship that is not expected to last, that is, the parts of the ship that are regularly exposed to water.
So, in the matters of identity, a change of parts is allowed and in fact, should be expected, but that does not imply a complete change of parts should be allowed. In fact, in any unique object, there exists something that differentiates it from the class of objects it is a part of, that is those parts that exist at the top of the hierarchy of composition, which make the unique object numerically the same after a change of parts. So, there does not need to be a limit on the proportion of parts changed, or even a limit on the changing of parts being done gradually. The identity of the object does not exist in the temporal parts that are expected to be replaced, but in the parts that both serve the purpose of the object and subsist throughout. To entertain my own conclusion to this problem, what would I say about The Ship of Theseus? Which parts of the ship are at the top of the hierarchy of composition? When, during it’s replacement of parts, is the ship no longer that of Theseus’s? It seems to me that we need to redefine The Ship of Theseus. The ship no longer belongs to Theseus as he, in the puzzle, is already dead. So, The Ship of Theseus should more aptly be named “The Ship on which Theseus Sailed”. The important part here is that the ship sailed and moved throughout the water. There is then some way of tracing this ships journey through time on the water as it is commandeered by Theseus. I would say the essence of the ship exists in a few irreplaceable parts that exist the way that they do by their history. The mechanisms relating to the wheel of the ship, the rudder, and the mast might tentatively be these parts which make the ship of Theseus. As Theseus gripped the wheel that moved the ship throughout the water while the mast held the sails that caught the wind. Surely, you can replace the rudder, the mast, the inner mechanisms, or even the wheel of the ship while still having that ship on which Theseus sailed, but these seem to be some of the elements at the top of hierarchy that were responsible for subsisting and for serving the strong purpose that the ship truly had, which is to take Theseus throughout the water. If everything that moved Theseus throughout the water is no longer a part of the ship, then you do not have The Ship on which Theseus Sailed. If you replace the wheel of the ship, you have less of Theseus’s ship. You would then have The Ship on which Theseus Sailed, but you do not have that which directed Theseus on his voyages. The same may be said about the rudder, but I would argue that the rudder belongs to the class of objects that is not expected to subsist throughout the lifespan of the ship as it is almost always expected to be underwater. In fact, the rudder is only expected to be out of water during expected repairs of the elements that are exposed to water, the process by which, lends some more credence to the fact that these parts are expected to be replaced and so do not hold value in the identity. The mast hold the sails. Without the mast then, you can have The Ship on which Theseus Sailed, but without that which held the sails. The sails may be different. I am tempted to call them a class of parts that are not expected to subsist, but they seem to hold some importance to the sailing of the ship. I would say this depends on whether or not Theseus ever had replaced the sails or had ever expected to have them replaced. Though I cannot reach much more of a verdict than this, I have shown that the essence of the ship exists in a variety of parts that hold weight with the purpose of the ship. I would then conclude that there are a few parts without which, you would not have The Ship on which Theseus Sailed. And so, Lowe is incorrect that “if we want to allow a change of parts at all, it seems that we must allow a complete change of parts”(26).
The puzzle of The Ship of Theseus is only one puzzle that arises out of the complex and pervasive nature of identity. It is one through which a serious discussion is warranted about the composite parts of an object through time, about hierarchies of composition, and about the effect that the past has on the future – but those are only a few of the many facets of identity. And only a few of the facets on which Lowe makes an error… Let’s talk about Tibbles.
The premises of Lowe’s argument are straightforward. First, “once a hair has definitely become separated from Tibbles, it is no longer a part of him”(37). It is easy to see that when we talk about the identity of Tibbles, this will necessarily include all parts that belong to him. For a part to belong to Tibbles, however, it seems that it must both be his own part and it must be, to some degree, attached to him. Practically speaking, if I were to ask someone to throw a rambunctious Tibbles into another room, he would not pick up the hairs left on the carpet and toss them in another room. So it seems to be common-sense that the hairs that have left Tibbles body are no longer a part of Tibbles. Further, whoever throws Tibbles into the other room is necessarily throwing all of the hairs attached to him into the room as well. We might, if we were cruelly inclined, talk about shaving all of the hairs off of Tibbles body, but even so we are only talking about removing a property off of Tibbles, a property that is a part of him. But what of the hairs on Tibbles that are “neither definitely separated from Tibbles nor definitely not separated from Tibbles”(37)? Lowe says that, for the hypothetical thousand of hairs that meet this criteria, there are at least a thousand good candidates for the true Tibbles the cat. Which one is the real Tibbles? Lowe and I would agree that we do not have to decide. The relation of part to whole, after all, Lowe says is “to a degree vague or indeterminate”(38). This is, however, where our agreement in this scenario ends. For Lowe says that “this does not commit me to saying that there is any vagueness in the relation of identity… since the relation of part to whole and the relation of identity are quite different relations”(39). Lowe defends this position on the basis of the persistence conditions of cat parts and cats. Cat parts, Lowe argues, are able to survive “the mutual separation of all of its members, but a cat cannot likewise survive if all of its parts are separated from one another”(39). Is this true? Obviously, a cat cannot survive the separation of all of it’s parts, but there seems to be two different definitions of survive in this context that Lowe is using in the same way. After all, cat parts are not alive, so talking about the survival of cat parts is necessarily different from talking about the survival of cats which require food and water. What Lowe is talking about is the persistence of identity here, but he gets it wrong.
Let me paint a somewhat gruesome picture. I might return home one day to find my cat somehow dismembered on my living room floor. I would not say, in this situation, that my cat is entirely gone, or that the identity of my cat has somehow been reduced into nothing. My cat is still my cat, it just so happens that he is dead and his parts are separated. But I might point to my cat there on the floor and cry “What happened to my cat?” The same would go for if I found my cat dismembered with each of his parts in a different room. I would still be able to refer to my cat as having been somehow dismembered and killed, but my cat still exists as my dead cat. It’s properties have changed, and rather substantially, but it’s identity survives. So how can there be “different kinds of changes that cats and collections of cat parts can and cannot survive”(39)? It seems superfluous to talk about cat parts as entirely distinct from cats. There are, after all, no cat parts without a unique cat from which they came. So it is not as easy as Lowe wants it to be to defend the notion that a collection of cat parts composing a cat is not a cat. So the same goes for Tibbles. We may be able to talk about a thousand potential candidates for Tibbles each with different cat parts; we may be able to form different sets of cat parts, but this does not lead to the conclusion that “they will have to compose different cats, since they are different collections”(39). Here is where Lowe gets hung up on his desire to keep some formal structure to the concept of an identity relation. Formally, we can talk about an identity relation as every element in a set being related to itself and itself only, or more formally R = {(a,a) | ∀a ∈ A} but this is mathematical set theory, which is based on the premise that we have formally defined identities in our world which, if we did, I would not be writing this paper. Here, it seems that Lowe is begging the question: He is invoking the formal definition of a mathematical identity relation to come to conclusions about identity. Obviously, there is great theoretical and practical applications to set theory, but it is a tool that uses a priori knowledge about identity which we simply do not have. So, I argue that there is, in the real world, a serious degree of vagueness in the relation of identity.
To conclude, let us return to Lowe’s formulation that, regarding the collections of cat parts on the mat, “why don’t they all compose cats? – in which case, they will have to compose different cats, since they are different collections”(39). The answer might not adhere to the strict definitions of mathematical set theory, but it doesn’t have to. For each of these collections of cat parts all compose the same unique cat, Tibbles. When I point to Tibbles shedding on the mat and say “look at that rambunctious cat, Tibbles”, everyone who has heard me knows very well to what I am referring. It might be the case that John considers the set of cat parts and hairs t1 to be the set that composes Tibbles, Jane might consider t2to be the set that composes Tibbles, and Lorba might consider the set t3to be that which composes Tibbles; nevertheless, t1 ,t2 , and t3 will all share the same elements at the top of Tibbles hierarchy of composition. So t1 = t2 = t3, and therein do we see the vagueness in the relation of identity, for when it comes to Tibbles, or The Ship of Theseus, or even ourselves, identity can only be so precise, but it can still be reasoned through to create a better understanding of our world.
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