Identity is a rather complex question and approaching it through reductionism is not useful, i believe. We living organisms are ships of Theseus, as already explained, and I don't think that we are our atoms because those keep changing all the time. Tokens are by definition replaceable. — Olivier5
There’s certainly a sense in which I’m not the same person I was 20 years ago. I’ve grown and changed as a person - new behaviours and attitudes, likes and dislikes, experiences and memories, and so on. And my material body is not the same that I had 20 years ago, with almost every cell dying and being replaced over time.
But then there is also a sense of continuity, and a linguistic practice of referring to my old self as being my old self. Unless you want to argue for something like a persistent immaterial soul, you can’t make sense of the truth of this by referring to some alleged mind-independent state-of-affairs that such considerations and claims correspond to. It can only be understood according to an anti-realist account (of meaning and truth).
May I ask: who is is interested in token sameness, and why? — Olivier5
They are of course two different glasses in terms of their material constituents and space occupied but people don't actually care for such considerations when they define and recognize things. — Olivier5
So, if you apply the word "same" at token level, Theseus left with a ship and came back with another, but if you apply the word at type level, he came back with the exact same ship that he left with. — Olivier5
Indeed, but they are all identical (isotopes aside) in terms of structure. — Olivier5
On an ordinary account of logic, if I assume
1) 2+2=4
2) if 2+2=4 then the cat is on the mat
Then it follows
3) the cat is on the mat. — Ennui Elucidator
Only types are definable though, tokens are not. You cannot define THAT particular atom of hydrogen. For any practical intent and purpose, it is the exact same atom of hydrogen than any other atom of hydrogen. — Olivier5
You can identify ships of a same kind though, by their name. The ship that left last week bears a different name than the one built today. Ergo they are recognizably and functionally different. — Olivier5
Things are not defined by their constituents, therefore, but by their structure and function. — Olivier5
As per your definition, note that you are not able to distinguish between a pile of wood pieces and a functional ship. As long as the material stuff is the same, it's the same thing, but what if the structure has changed and the material hasn't? Is it still the same ship then? Is a pike of wood piece taken of a ship equal to a ship? No it ain't. — Olivier5
In my definition, structure has to remain similar if not absolutely identical. — Olivier5
I think of it as about mind-independent structure and behavior. That's more practical in my experience. — Olivier5
It doesn't really matter, other than in your mind experiment. They are the same model, bhave the same way; not distinguishable. Who cares which is which? — Olivier5
Speaking very roughly, just to get started, realism holds that ...stuff... is independent of what we say about it; anti-realism, that it isn't. — Banno
That's specifically the issue - does it count as one ship or two?
And "count as..." is a lexical marker for issues of convention. — Banno
Yep, you are. But you are making a conclusion about realism from that. What is your argument for that conclusion? — Banno
Objective features of the world change, and yet the ship that returns is the ship that leaves. It's not the same physical stuff, but it's the same thing. That it's the the same thing is a conceptual/linguistic imposition, a way we view and talk about the world. That's anti-realism. There is no mind-independent fact that determines it to be the same ship. A realist is committed to say that it's a different ship, as the material that leaves isn't the material that returns. — Michael
If we don't see it as the same ship because it's now a plane then it's not the same ship because we don't view it that way. If we don't see it as the same ship because its parts have been replaced (even with similar parts) then it's not the same ship because we don't view it that way. If we see it as the same ship because its parts have been replaced (with similar parts) then it's the same ship because we view it that way. — Michael
On the one hand we have the realist who says that statements are made true by objective features of the world, but what objective features of the world must obtain for the ship that leaves to be the ship that returns? Presumably that the mind-independent material stuff that leaves is the mind-independent material stuff that returns. Which in this case doesn't obtain, and so the realist must commit to "the ship that leaves is the ship that returns" being false. However that might not be a commitment the realist is willing to make, and so they must accept an anti-realist account of "the ship that leaves is the ship that returns" being true; that it's true because we think of the ship that leaves as being the ship that returns. — Michael
Only when we use the term in a way previously unintended do we run into these challenges — Hanover
So to make it simpler, let’s say the ship that left was named the Theseus and that along with the part-replacements they adopted the name the Perseus.
Was the Perseus previously known as the Theseus?
That's specifically the issue - does it count as one ship or two?
And "count as..." is a lexical marker for issues of convention. — Banno
"The ship that left is the ship that returned" is true if we define "ship" in terms of functionality. It is false if "ship" is defined as that which contains all the same boards. — Hanover
This isn't a rejection of bivalence. This is just pointing out certain words are vague. — Hanover
You're claiming that what a 40 year old is cannot be determined because there is no single truth value to the statement "a 40 year old is X."
What, specifically, is the difference between these? — Banno
For your idea to be 'true and false' you require a narrative description because the departure and arrive are two separate events over time. Would this not be the same thing as saying a human being is both young and old? — Tom Storm
Provide an example of a statement that is both true and false. Are you saying within exact contexts and with exact definitions the same statement can be both true and false? — Hanover
Good point. I assume you mean that these are "thigns" and "true" or "false" cannot be applied to them. Right, TiredThinker made a mistake in not specifying what kind "things" he is talking about. Most probably he meant "statements" ... — Alkis Piskas
People are real. — Olivier5
A semantic realist, in Dummett’s sense, is one who holds that our understanding of a sentence like (G) consists in knowledge of its truth-condition, where the notion of truth involved is potentially recognition-transcendent or bivalent. To say that the notion of truth involved is potentially recognition-transcendent is to say that (G) may be true (or false) even though there is no guarantee that we will be able, in principle, to recognise that that is so. To say that the notion of truth involved is bivalent is to accept the unrestricted applicability of the law of bivalence, that every meaningful sentence is determinately either true or false. Thus the semantic realist is prepared to assert that (G) is determinately either true or false, regardless of the fact that we have no guaranteed method of ascertaining which.
...
According to the constitution thesis, the literal content of realism consists in the content of semantic realism. Thus, the literal content of realism about the external world is constituted by the claim that our understanding of at least some sentences concerning the external world consists in our grasp of their potentially recognition-transcendent truth-conditions. The spurious ‘debate’ in metaphysics between realism and non-realism can thus become a genuine debate within the theory of meaning: should we characterise speakers’ understanding in terms of grasp of potentially recognition-transcendent truth-conditions? As Dummett puts it:
"The dispute [between realism and its opponents] concerns the notion of truth appropriate for statements of the disputed class; and this means that it is a dispute concerning the kind of meaning which these statements have (1978: 146)."
If one is realist about structures, then people can realistically be understood as semi-permanent mind-independent structures — Olivier5
Yes, but they are the same model of ship and one could be hard pressed to distinguish one from the other.
My point is that structures are something we recognize as real. Reality is not just matter, it is also in how this matter is bound together in a whole and how they function when thus binded, how the whole behaves as a whole. — Olivier5
Consider Theseus himself. During the trip, an estimated 90% of his own material constituants have changed. Water drunk and sweat, proteins eaten and used then decayed and excreted... Our body is always in flux. The boat of Theseus is us. And what Aegeus would have recognized as his son was not this or that set of molecules, but a structure binding them in a whole: his son's features, voice, manner of moving and speaking. Not his precise chemical composition.
According to Hilary Putnam, the metaphysical realist subscribes not just to the belief in a mind-independent world but also to the thesis that truth consists in a correspondence relation between words (or mental symbols) and things in that mind-independent world. Call this thesis correspondence truth (after Devitt 1991).
...
A much stronger anti-realist argument due to Putnam uses the brain-in-a-vat hypothesis to show that realism is internally incoherent rather than, as before, simply false. A crucial assumption of the argument is semantic externalism, the thesis that the reference of our words and mental symbols is partially determined by contingent relations between thinkers and the [mind-independent] world. This is a semantic assumption many realists independently endorse.
Given semantic externalism, the argument proceeds by claiming that if we were brains in a vat we could not possibly have the thought that we were. For, if we were so envatted, we could not possibly mean by ‘brain’ and ‘vat’ what unenvatted folk mean by these words since our words would be connected only to neural impulses or images in our brains where the unenvatteds’ words are connected to real-life brains and real-life vats. Similarly, the thought we pondered whenever we posed the question “am I a brain in a vat?” could not possibly be the thought unenvatted folk pose when they ask themselves the same-sounding question in English. But realism entails that we could indeed be brains in a vat. As we have just shown that were we to be so, we could not even entertain this as a possibility, Putnam concludes that realism is incoherent [Putnam 1981].
It is the same ship because it is structurally the same ship, or close enough to the original structure. — Olivier5
And this mainly for Texan women or women anywhere cut off from access to legal abortion. If men can control a woman's body, then as counterbalance she gets a firm grip on his wallet. — tim wood
The ship leaves port. The mast is replaced, then the keel; the various planks of the hull are replaced. At each step something is taken and something replaced. Take out the word "objective" and it's clear that the ship that leaves is the ship that returns" is made true by features of the world. — Banno
This raises an interesting point to Michael's claim. If we replaced each plank one at a time, but with planks dissimilar enough from the original that the ship returned an airplane, we'd be hard pressed to call it the same boat. The material composition then matters, which means that external reality is critical for identity. — Hanover
