I think it's time to move on to the next lecture - "Pleasure". I'll post it as soon as I can.

If the criteria for establishing identity are physical, — Janus

That's a big "if". I would have thought that the criteria most important to most people are social - and even when they are physical, they often also have social connotations.

Whether those DNA patterns can change, as physiognomy obviously does would not seem to matter. — Janus

Changes in actual DNA are mutations and part of what's going on, but not, I would have thought a major part. At least, I had in mind the point that the way that DNA is expressed often depends on environmental factors. I have seen it is claimed that there is as much reason to say that we are products of our environment as products of our DNA. The idea that everything is down to DNA is an over-simplification that panders to our essential inclinations that DNA is the essence of what we are.

but the details will not be exactly the same in any two cases, — Janus

I won't argue with you. But isn't that an empirical claim, which it is difficult to impossible to refute. Isn't the real truth that the probability of an two leaves being identical is very, very small. But still, it can't be ruled out completely. When you get down to brass tacks, the same is true of DNA.

If that is the case then to say anything stays the same is a fallacy and it would also make the term is/change identical. — I like sushi

The Heraclitean/Bhuddist idea that everything changes is the obverse/reverse of the claim that everything stays the same. As your next sentence shows, the truth is much more complicated than either. The mistake is to fasten on one view as The Truth and not to pay attention to what is really going on, which is a mixture.

I will have to consider more subtleties like this into my view. — Apustimelogist

I think my favourite complexity is the one about the non-coding bases, which are 98% of the molecule. What is all that stuff doing there? I don't believe it is doing nothing. The question is, what is it doing? Talk about terra incognita

It doesn't make any logical difference.

Would "Achilles runs faster past smaller distances" cover it?

For example, if the sperm that "won the race" in your case had not made it, someone else, not you, would have existed in your place; — Janus

This is where the third person view helps. Since I wouldn't have existed, how would we know that the replacement wasn't you? Equally, then, how do we know that the proposed minor variation - even if it caused a massive difference - would have been at all different from me? It's based on the assumptions 1) that the DNA would have been different in some way that made a difference to the result and 2) that every difference is equally important.

Absolutely. But it's interesting, because it is very unlikely that one will again come across the exact same chess position, and be able to make a different choice in the exact same situation, and yet one learns how to look, and how to analyse other positions and make other choices better. So counterfactuals function as useful notions here. — unenlightened

All of that is true. But the important thing here is that although one may never encounter the exact some position again, the process of analysis can reveal similarities among those differences. Some of them will matter, and some will not. When one can do that, one can learn from past experience. But if every difference is equally important and equally makes a position different in the sense that past experience is irrelevant, then past experience can teach you nothing.

If I had been a soldier in Cromwell's army, then necessarily the right sperm and egg would have miraculously come together at the appropriate time to make that happen. — unenlightened

I like that answer. Very neat.

The genes obviously contribute but seems intuitive one might change genetic information or phenotypic traits of a person and retain the identity. — Apustimelogist

It is well established that the links between genes and specific characteristics are very complicated and often surprising.

"A large part of DNA (more than 98% for humans) is non-coding, meaning that these sections do not serve as patterns for protein sequences." From Wikipedia article - "DNA"
From this it follows that a random variation in one base of the molecule is unlikely to cause a variation in the phenotype.

Here are some more complications:-
"Many features of a phenotype result from more than one genetic modification. An organism's phenotype results from two basic factors: the expression of an organism's genetic code (its genotype) and the influence of environmental factors. Both factors may interact, further affecting the phenotype." from Wikipedia - "Phenotype"
"When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever colouring; while the coat colour depends on many genes, it is clearly seen in the environment as yellow, black, and brown." Wikipedia - "Phenotype"
"A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome. The mutation responsible can occur spontaneously before embryonic development (a de novo mutation), or it can be inherited from two parents who are carriers of a faulty gene (autosomal recessive inheritance) or from a parent with the disorder (autosomal dominant inheritance). When the genetic disorder is inherited from one or both parents, it is also classified as a hereditary disease. Some disorders are caused by a mutation on the X chromosome and have X-linked inheritance. Very few disorders are inherited on the Y chromosome or mitochondrial DNA (due to their size)." Wikipedia article - "Genetic disorder"

It is pretty clear. Piece by piece if every part is replaced it is still ‘the original’ as it is their ship. Someone collecting and reassembling the parts produce their own ship not someone else’s ‘original’ ship. — I like sushi

Well, I'm not sure about that, but it seems to be the standard answer these days. What I was after was the doctrine that any change, not matter how small, make it is different ship, or a different person.

it is very instructive to go through an old game of one's own with an experienced player who can point out problems one had not seen and possibilities one did not consider, — unenlightened

Quite so. I think the difficulty here is that if one is looking forwards, possibilities could become actual. But if one is looking backward, they could not. If one then says that the moves one actually made are now necessary, it looks as if someone is trying to deny that what was a possibility then, is not a possibility now. If that were true, one could not consider them after the game. Which is absurd.
The idea that what is, is necessary is an exaggeration of the familiar point that a move that was possible in the middle of the game can no longer be made after the game is over.

In terms of counterfactual scenarios, though, I think schopenhauer1 is correct to say that, in consideration of the genesis of any particular organism, any circumstances which would have produced a different genotype at conception, would result in a different entity existing. — Janus

But then, any circumstances after conception that affect the development of the DNA will also result in a different entity existing. Surely? The development from DNA to person is not a railway track, but a path through rough country - to an indeterminate destination.

The fact that, on this account, the DNA is a necessary condition, but not sufficient, allows for the possibility that there are other conditions that could have produced the same result. No?

Yes, I get the intuition. It seems to make sense, more from the causal link standpoint than the blueprint one because I am not sure that DNA can be identified with us as opposed to picking out us in a way that is somewhat incidental. — Apustimelogist

Well, a DNA molecule is not a person, so it seems clear that the identity of the molecule is not equivalent to the identity of the person. The DNA molecule is not the resulting person, but one of the causal conditions that produces that person. But then, some people think that causal conditions are necessary, which seems to me to abolish the meaning of "contingent" and so deprive "necessary" of its own meaning.

There is nothing here and I confused why there is a needless back and forth debating why YOU is important as some non-existent being that is never non-existent because YOU exist. — I like sushi

I think that's why it is important not to frame these issues by reference to the first or second person. They are a lot clearer if one asks the questions in the third person.
The other thing that muddles this debate up is the idea that if Theseus' ship has the tiniest, most unimportant part of itself replaced, it is a different ship. Surely we all know that the point at which the changes to the ship make it a different ship is not clearly defined.

Here's a link for a download Austin "Sense and Sensibilia"

Lecture VII pp. 62 - 77.

I hope you find it enjoyable and profitable.

Thereby hangs a PhD - or a career. — Banno

Thank you. I'm not the person to do that work. I think I'll remain respectfully sceptical.

Oh, I'll say it is correct - it's not wrong. But unfulfilled - yeah, ok. — Banno

Correct/wrong is a very intricate issue. Complete agreement is hard to find. But is his doctrine right enough to resolve the fatalist's argument?


I agree with what you say. My version of this is that Achilles may have to pass an infinite number of points to pass the tortoise, but he has the advantage that he can pass each point in an infinitesimal amount of time.

I don't think talking in this way invokes any ontological mystery. — Banno

Well, if my attempt involves ontological mystery, I'll give up on it.

I think it true that there will be an eclipse in March, 2025. — Banno

I'm glad that you don't think that it is like Hume's failure of the sun to rise tomorrow morning, which, it seems, will affect nothing else.

I agree that it is true that there will be an eclipse in March 2025. I suggest however, that the prediction that there will be an eclipse in March 2025 is neither correct nor incorrect, neither fulfilled or unfulfilled until April 2025. Will that do?

Because of the lack of volition? — Banno

I've been thinking about precious little else for hours.

Since Kripke, It ain't necessarily so. — Banno

Very good. The prospect of an infinite regress of necessities is positively intimidating.

But seriously, who invented this idea, and is it proof against Humean scepticism? If not, why not?

If you do a search you will find several articles that credit Zeno. — Fooloso4

OK. It is certainly possible that he was, and it is hard to be sure of anything about those very early philosophers. It just seems so odd that an argument that seems quite clearly to establish a conclusion should actually be intended to keep ideas in play. I suppose an argument for an absurd conclusion could be intended to provoke a response, rather than to establish a truth. But we'll never really know what Zeno intended.

An apparent dig at Austin...? — Banno

I find that hard to believe. Austin puts a lot of emphasis on the inter-connectedness of words. Austin would certainly consider "cause" and all sorts of related words at the same time, bringing out their differences and similarities, wouldn't he?

But then, a dig doesn't have to be fair.

I've been unable to follow what Ryle means here by "general" and "singular". — Banno

Ryle does preface his articulation of the idea with "roughly", so it wouldn't be surprising to find deficiencies.

I got worried about that and came up with this:-

I'm bothered about someone having a heart attack, and getting to hospital where they prevent his death. Can we not say that his death was averted? Perhaps we can say that it was averted last Sunday, but not that his death last Sunday was averted. — Ludwig V

But I can't work out a similar tactic for the lunar eclipse. The best I can do is a gesture. The eclipse is predictable, but does not yet exist (is not actual). When it happens, it will become real/actual and when it is over it will have been real/actual.

(My apologies to Austin. I couldn't think of a better way of putting that.)

You could say that the job of a counter-factual is to consider impossible possibilities.

It was a genuine question. I don't know what causal necessity means. I know what "I inherited my fair hair from my parents means." But then, I've been reading Hume.

Yes, but I see no reason to take such a view seriously. — Banno

I've discovered that I'm a bit prone to being distracted by side-issues, so I won't ask what that means.

Dialectical movement does not resolve things, it keeps them in play. — Fooloso4

I'm puzzled. I thought Socrates/Plato invented dialectic. What's the evidence that any pre-Socratics knew about dialectics?

And did Kripke invent causal necessity as well?

But, supposing I am the first child of my parents, there would still be a first child. Why wouldn't that be me, but different?

I happen to know that they intended to call their first child Ludwig if it was a boy. I forget what the choice would have been if I had turned out to be a girl.

And then, presumably, the name Ludwig would have rigidly designated their first child if it was a boy, or their second if that was a boy and so on. Then gametes would be irrelevant.

That is similar to Kripke's causal-theory of proper names and use of rigid designators. — schopenhauer1

You say that as if it settled the matter. Is there a universal consensus that Kripke is necessarily right? That would indeed be remarkable.

But when discussing the past, it's always going to be in relation to the YOU existing now. — schopenhauer1

In a sense, yes. Which is why I went back to the past before I existed - when there was no me for anything to be in relation to.

To put the point another way, if any discussion about the past is always going to be in relation to Ludwig V, is it always going to be in relation to schopenhauer1, my sister Mary Anne and the postman. Why am I so special?

Zeno provides the arguments. — Fooloso4

Quite so. But if he was misled, doesn't that suggest that the conclusion of the argument is wrong, or at least may be wrong? Does that really make no difference?

Well, bits of metaphysics that I can never know do not concern me greatly. I'm funny like that.

The person Ludwig V is linked "as an individual person" by way of causal instance of gametes combining. — schopenhauer1

If the link is causal, it is empirical. Which means it is not necessary.

It would have been someone else. — schopenhauer1

How could it be someone else if I don't exist?

It is impossible that I moved the bishop and won the game, because I moved another piece and lost. — unenlightened

So maybe I considered moving the bishop and decided to do something else. When I did something else, it was no longer possible. But it was possible when I considered it. Surely?

It makes a difference because indeterminate future is one without you. The five minutes changes the gamete to someone else’s genetics. — schopenhauer1

No, it does not. Because the person who would have been born 5 minutes earlier never existed and never could have existed. There's only person one who exists. You can say that there are possible people who would have existed if I had been conceived 5 minutes earlier or 5 minutes later. But you can't say anything about them, not even whether they would have been the same or different - except by arbitrarily stipulating that they would. Where would your evidence be for saying that they were the same as me, or different from me in ways that matter or different from me in ways that don't matter?

I'll sort something out for you. But that's only about "real" and "reality". The bit about concepts is my own invention.

You frame this issue as "... but that wouldn't have YOU". In brief, I think the issue is partly created by the way it is framed. Given that I exist, my possible supposition that my gametes could have been different from the ones I actually have is hampered by the absolutely certain fact that they weren't. If the question was differently framed, I think it would get a different answer. Suppose you are a parent trying to make a baby. Do you seriously think that whether you performed the action 5 minutes ago or in 5 minutes time matters. You may realize that there may be some differences - even serious differences, but do they make any difference? I don't think so. The difference is that there's no me to make any difference. (cf. Ryle)

But then this brings up ideas of different causes for the same outcome. — schopenhauer1

Yes. Isn't that implicit in "necessary but not sufficient"?

How much does the limit have to reach 100% for it to considered a necessity that everything had to be exactly the same? — schopenhauer1

I would say it has to reach at least 100%. But maybe you don't?

using a rigid designation. — Banno

I wish I had thought of that days ago. But I'm not sure it applies. Doesn't Ryle's argument about the future mean that rigid designators cannot be rigid in the future tense?

this is not some fantasy world for Zeno, — Richard B

That's certainly true. I didn't distinguish carefully enough between Zeno's thinking and ours. We have the benefit of an established distinction between theory and practice, which didn't exist in Zeno's time.

All I am saying is experience settles some questions not just lingustic analysis. And in this case, experience should be arbiter. — Richard B

That's true. It would be interesting to know why you think that experience should be the arbiter in this case. By the way, I don't think that anyone thinks that Achilles won't overtake the tortoise.
Experience isn't a given. It needs interpreting. You experience the sun coming up over the horizon on Monday morning. You have the same experience on Tuesday morning. What tells you that it is the same sun and not a new one every day? How do you know that the sun doesn't rise, but the earth turns?

it should be to ask why would anyone be tempted to take this serious to begin with. — Richard B

Well, Zeno did. So have many other people. If you want to know why, read Ryle.

I think that the best answer to what you are saying is that the paradox isn't a problem. It's a puzzle. Whether it's a serious puzzle or not is another question. Whether it's an interesting puzzle is yet another question.

We can't name the individual accidents that were avoided, but can still maintain that the overall probability of an accident was reduced. — Banno

Yes. That's because, of course, there are, ex hypothesi no individual (actual) accidents to be averted. I don't see that Ryle is at all confused here.

Clearly, we have an answer to the problem of who will win the race between Achilles and the Tortoise. — Richard B

Surely, you are missing the point here. No-one doubts who will win the race. The question is how Zeno makes it appear that there is some question about that. The answer is that he considers the race from a certain, misleading, point of view. Ryle's project here is to understand how that illusion is created. Wittgenstein speaks of conjuring tricks. Austin, in Sense and Sensibilia has similar, but less brutal, descriptions of the process.

He says, “Yet there is a very different answer which also seems to follow with equal cogency from the same data.” But what “data” is that? — Richard B

Ryle is not always precise in his language. "Data" just means the set-up of Achilles racing the tortoise

which are not rival solutions of the same problem, but rather solutions or would-be solutions of different problems, and which, none the less, seem to be irreconcilable with one another.” — Richard B

Yes, I think that's exactly what Ryle is saying about this problem.

So, why did Ryle not just declare a winner and be done with it? — Richard B

Well, he wants to diagnose why anyone would have taken Zeno's problem seriously - and, by the way, Zeno also took this problem seriously in that he believes that all change, including motion, is an illusion.
I think there is a real problem here, and it needs to be acknowledged. You can calculate the time it takes for Achilles to complete the race and for the tortoise to complete the race, you; you can then compare the times and see that Achilles will win. But if you ask when (or where) Achilles will catch up and pass the tortoise, you can't - not accurately, as you can with the first calculation. The consolation prize is that you can calculate it to any degree of accuracy you like; but that didn't become possible until the calculus of infinitesimals was invented in the 17th century CE.

To actual cake, or some abstract object call “a cake”? This is where I think Ryle presents a confusing picture. — Richard B

Yes, Zeno's problem is purely theoretical not, in some sense of the word, real. Which is why it is so tempting to simply declare the winner.

But Ryle wants to say something additional, Zeno is putting forth an abstract platitude. But I say Zeno parades a metaphysical fiction disguised as a scientist hypothesis. — Richard B

Well, yes. Zeno does have a metaphysical solution to the problem, which is to declare motion impossible. Philosophy has progressed to the point where we don't need to argue about that any more. Who says philosophy never makes any progress?

Oh by the way, what I am discussing versus a specific identity versus a general future event, is not so indirectly related to this passage in Ryle: — schopenhauer1

Yes. That puts a different perspective on things. Very helpful.

Here's my summary/reconstruction of lecture III on Achilles and the tortoise:-

The first part of the third lecture is about a real chestnut. But it is rather hard to follow, in the sense that it is hard to see where he is going. I think it helps to start with his conclusion, his diagnosis of the problem.

His final remark is not a surprise – “Similarly (i.e. to the fatalist’s dilemma) here we have been talking, so to speak, in one breath with the sporting reporter of a newspaper, and in another breath with our mathematics master, and so find ourselves describing 1) a sprint in terms of numerators and denominators and 2) of relations between fractions in terms of efforts and despair.” p. 53 (numbers and strikethrough mine).

On the previous page (52), we find the specifics – “We decide factual questions about the length and duration of a race by one procedure, namely measurement; we decide arithmetical questions by another procedure, namely calculation. But then, given some facts about the race (such as whether Achilles will win) established by measurement, we can decide other questions about that race (such as where and when Achilles will overtake the tortoise) by calculations applied to these measurements. The two procedures of settling the different sorts of questions intertwine, somehow, into a procedure for establishing by calculation concrete, measurable facts about this particular race. We have the pony in the harness that was meant for any such pony, yet we can mismanage the previously quite manageable pony in its previously quite manageable harness.” His summary his helpfully simpler – “Two separate skills do not, in the beginning, intertwine into one conjoint skill.”

(I think this is his gesture towards the mathematical solution of the problem by application of the calculus which demonstrates that we can calculate when Achilles will overtake the tortoise to any level of accuracy that we desire).

Going back a bit further he acknowledges the common ground between the two skills (p.48) “… in an important way we are, in all applications, thinking in terms of or operating with the same overarching notions of part, whole, fraction, total, plus, minus and multiplied by.” He articulates the question (p.50), as “How is (what we know quite well about the stages of an athlete's victorious pursuit) to be married with (what we also know quite well about the results of adding together a fraction of a whole, that fraction of the remainder, that fraction of the next remainder, and so on)?”

He partially answers this question by pointing out:-

1) that “never” in this scenario is ambiguous between the harmless truism “To say this (sc. that the sum of 1/2, 1/4, 1/8, 1/16 etc., never amounts to unity). is simply to utter the general proposition that any particular remainder-bisection leaves a remainder to bisect.” and the alarming prophecy that “if a silly computer were to attempt to continue bisecting remainders until he had found one which was halved but had no second half, his attempt would then go on to all eternity.” p. 50/51.
He also, less transparently, finds an ambiguity between “all” as in the total when all the parts are added up and “any”. I don’t quite understand it and cannot find a suitably brief quotation.

So that’s my backwards summary of the part of his lecture that begins on p. 48 with:- “Now let us draw some general lessons from this dilemma.” Returning to the beginning, Ryle’s aim is getting us to see that the paradox hypnotizes us into seeing it only as an endless series. We need to appreciate two distinct points of view. One is the overview of the whole event (by a non-participant) and the other is the narrow view of a competitor in the race. He approaches this by considering dividing up a cake alongside dividing up the race. I think the point is that in dividing up the race, we tend to forget the overview of the whole; it is easier to keep the whole cake in mind because it is not a temporal process. Some of the points that I found helpful:-

1) On p. 42, he imagines that we might mark out the course by planting a flag at each point of the calculation. At the half-way mark, the quarter-way mark and so on. The method itself guarantees that there will always be a place for another flag, so we think that Achilles will never reach the tortoise. But if we reversed the process, would we be convinced that the race did not have a beginning?

2) “Similarly Zeno, in his mentions of the successive leads to be made up by Achilles, is, though surreptitiously and only by implication, referring to the total two-mile course run by Achilles in overtaking the tortoise; or in other words, his argument itself rests on the unadvertised premiss that Achilles does catch the tortoise in, say, precisely two miles and in precisely one hour.” p.44.

3) We need to see that there is a crucial difference between two questions – “To put a central point very crudely, we have to distinguish the question' How many portions have you cut off the object?' from the question 'How many portions have you cut it into?’”. (p. 46) In the first question, we have partly cut the cake and there is always part of it left. In the second question, we have cut the whole cake up.

I agree with you. The only thing I would add is that it is a surprise, at least to me, to realize that "While it, is still an askable question whether my parents are going to have a fourth son, he cannot use as a name the name 'Gilbert Ryle' or use as a pronoun designating their fourth son the pronoun 'he'. Roughly, statements in the future tense cannot convey singular, but only general propositions, where statements in the present and past tense can convey both. More strictly, a statement to the effect that something will exist or happen is, in so far, a general statement. When I predict the next eclipse of the moon, I have indeed got the moon to make statements about, but I have not got her next. eclipse to make statements about."

What is new to me is the idea that the future tense is different from present and past because we cannot refer to things that do not yet exist.

That's fine by me. These summaries - at least in the case of this book - are not that easy to do, so I will appreciate having some extra time. That doesn't mean I don't appreciate your comments, for which I thank you.

So does this mean that the idea that I might have been a musician, or an accountant, or a Roman Catholic, are all nonsense? Odd, don't you think? Might have I had fair hair or blue eyes? Could I have married someone else? Might my children have turned out to be criminals or saints? It's all very peculiar.

DNA matching is indeed the gold standard of identity, but only in the way that fingerprints are a silver standard and facial recognition a bit unreliable. That is, DNA was identified and installed as an empirical criterion, not a conceptual criterion.

To put it another way, DNA is part of the story about how I came to be - a cause. So perhaps you are picking up on causal determinism? But it is not the whole story. What happens to me while I am growing plays just as important a role as DNA. Compare an oak tree. It starts from DNA, but the tree that it becomes depends also on how it grows in the environment that it happens to be in. If the acorn had landed elsewhere, it would have been a different tree. Perhaps we can agree that DNA is a necessary, but not sufficient, cause of a new person being created, thus recognizing that other factors play their crucial parts.

And then, that body or mind is subject to changing experiences that could alter the course of their outlook, life, personality, etc. — schopenhauer1

This is very helpful. It indicates that the foundation of personal identity, for you, is spatio-temporal continuity in the narrative of a life. If that's right, then you are denying that people who undergo changes that they think they have become a different person are simply wrong. I admit that is a bit problematic, but I don't see how you can dogmatically rule that out. Perhaps we need to think more carefully about what being a person is, and how it is something different from being a human being.

But if people can change in the course of their life, without those changes being so radical that they become a different person, what makes the gametes so important and sensitive that ANY change in them produces a different person. It seems absurd to suppose that if I was conceived 5 minutes earlier or later, the resulting person would not be me.

His particular style of writing feels like a lot of foreplay without a crescendo. — Richard B

I'll do my best. As to the problem with his style, I can understand that would be disappointing. Perhaps my introduction should make it clear what the climax is.

I can't say this thread is working very well, but if two or three people are interested and actually reading the book, I'm perfectly happy to continue.

It is pretty clear that there is no reaction to lecture I, so I'm thinking of moving on to lecture II.

But I need some guidance, particularly from you, Antony. Are you cogitating any comment on lecture I? If so, I'm happy to wait. If not, perhaps it is time to move on.

So being of the same gametes is necessary but perhaps not sufficient to identity. — schopenhauer1

I did read it. But I guess I didn't pay enough attention to that last sentence.

Well, you are slightly moving the goal post. — schopenhauer1

That's what a discussion is about, surely. Listen to the other guy, adjust your view and on we go. With luck, we might even reach agreement!

However, we have some way to go, and I'm a bit concerned that this issue is clearly off-topic. One of us could start a different thread, and I think that would be a good idea. How about it?

I'll wait for you reply before actually replying to that message. You won't be surprised that I have a good deal to say.

For the moment, I notice that you don't say that the fertilized egg is me; I'm assuming that you mean that it is the origin of me.

And in response to

All I am establishing is that if the gametes are different than the one that was your set of gametes, whatever the case may be (whether they are similar to you or not), THAT person who was conceived a second before or after with different gametes is not you. — schopenhauer1

That can't be true. A clone of me (such as a possible identical twin) would not be me, either. And if you look carefully at what is written about DNA, there is a possibiity (several million to one) that someone else might be born with the same DNA as me.
I admit that DNA is treated as a unique identifier for me. But this is an empirical relationship, like the supposed unique pattern of my fingerprints (or, I understand, my palm-print or ear-print). I mean that the uniqueness of DNA was established on the basis of our understanding of personal identity. So it doesn't establish any logical relationship.

Anyway, let me know about the new thread.