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

The combination of the DNA code from the set of gametes. The fact that this has slight changes over time or whatnot does not invalidate this. — schopenhauer1

Agreed, but then it's just an historical fact about you.

it can't be any set of gametes, it has to be that set and not another. — schopenhauer1

Sure, but can't we say the same about all the facts in your personal history?

If you went back in time and encountered your younger self, you would consider that youngster a person distinct from yourself. If youngster stubbed his toe, only he would feel immediate pain. I account for the distinction in terms of histories: your history differs from youngster's, even though there's overlap.

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 — Ludwig V

Well, not really terra incognita, because stuff is being learned about non-coding DNA. One such detail (and actually kind of old news) is that broken down genes for the production of egg yolk components occupy some of that DNA.

Embryonic development in nonmammalian vertebrates depends entirely on nutritional reserves that are predominantly derived from vitellogenin proteins and stored in egg yolk. Mammals have evolved new resources, such as lactation and placentation, to nourish their developing and early offspring. However, the evolutionary timing and molecular events associated with this major phenotypic transition are not known. By means of sensitive comparative genomics analyses and evolutionary simulations, we here show that the three ancestral vitellogenin-encoding genes were progressively lost during mammalian evolution (until around 30–70 million years ago, Mya) in all but the egg-laying monotremes, which have retained a functional vitellogenin gene. Our analyses also provide evidence that the major milk resource genes, caseins, which have similar functional properties as vitellogenins, appeared in the common mammalian ancestor ∼200–310 Mya. Together, our data are compatible with the hypothesis that the emergence of lactation in the common mammalian ancestor and the development of placentation in eutherian and marsupial mammals allowed for the gradual loss of yolk-dependent nourishment during mammalian evolution.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267819/

Another stretch of DNA is a broken down version of what once was a gene for producing Vitamin C.

Other details involve stretchs of DNA which can promote or inhibit the transcription of coding DNA.

I'm far from having any expertise on the subject, but my impression is that it would be a rather daunting task for most to come up to speed on what is understood about noncoding DNA these days.

Sure, but can't we say the same about all the facts in your personal history?

If you went back in time and encountered your younger self, you would consider that youngster a person distinct from yourself. If youngster stubbed his toe, only he would feel immediate pain. I account for the distinction in terms of histories: your history differs from youngster's, even though there's overlap. — Relativist

Sure we can split every nanosecond into its own time slice and call that a different person. Same with any object. Yes, time adds duration and development to that object, but the element of change, doesn't mean each unit of change is a different object. Why is it that you are not a rock or a grain of sand or a computer or another person, a bat, a wolf, an insect, or a molecule floating in the air? It's not because of some temporal aspect of things, except in the point in time it matters, when the two gametes combined. Whatever else happened, that is what started the person to be, which is why I put it as a contender as necessary for someone to be someone, even if not sufficient for full identity.

I will add of course, that those hypothetical questions should not be taken as you could be anything else. That was my original point, there could never be a counterfactual case where you could have been something else (prior to conception)... and hence the case that indeed it is when the gametes meet that is the start of how "you" are you. Development of course can add and does add to this identity.

Curious did you have an answer for this?
https://thephilosophyforum.com/discussion/comment/862434

This is another topic, but this kind of parallels our debate for why it matters whether one has achieved some "unity" of this monism (aka Nirvana), or nothingness. What if there were no lifeforms, as was the case prior to 4.5 billion years ago, give or take? Energy and matter on their own don't seem to need liberation from anything. It seems at the least, the problem is biological as much as it is existential, as existential matters not without the biological. And thus, this is contra to the always existing mind of idealism. — schopenhauer1

The post of mine you were responding to was tangential to the topic so I didn't pursue it. It was written from the perspective of Vedanta where 'the self' is understood as 'the self of all beings'. This intuition harks back to Alan Watts' book The Supreme Identity - hence the connection with 'identity'. (That book was an early influence of mine.)

As to the 'always-existing mind of idealism'. Your question is phrased from the naturalistic perspective, which understands the mind as an emergent or evolved capacity, or at any rate, something that only comes into existence as a result or consequence of evolution, as a product of material or natural causes. Philosophical spirituality (if we can call it that) looks at the matter differently, although it's somewhat difficult to articulate in today's terms. To put it in Watts' terms, in referring to "The Supreme Identity," he is talking about the idea that at the deepest level of reality, there is no fundamental separation between the individual self and the universe. It is the recognition that the distinction between "I" and "the world" is ultimately an illusion. Instead, there is a unitary being, the 'supreme identity' that underlies and encompasses all of existence. In this context, the individual ego or self is seen as a construct, a temporary and illusory identity that we create (very deeply!) in our minds. To discover the supreme identity is to recognize that our true nature is not limited to our individual ego but is interconnected with everything in existence. It's a profound shift in perception and consciousness, which transcends the boundaries between self and other, subject and object. It is emphatically not non-being or non-existence although it seems it must be that to the egoic consciousness. (Although his book is primarily based on Eastern philosophy Watts does also discuss the idea of divine union in Thomas Aquinas. You do find parallels, at least, in some schools of Christianity, especially Christian mysticism, but these kinds of ideas have a rather uneasy relationship with mainstream Christianity, hence the constant tendency of the Christian mystics to run afoul of ecclesiastical authority.)

But again, quite tangential to the OP.

But again, quite tangential to the OP. — Wayfarer

Indeed, but I asked for clarification, so thanks for that. I question your assertion that the individual is illusory other than that it is a grandiose way of saying it is constructed from experience. But that is a common psychological view. However, I think you are going a step beyond this and saying that there is a greater existence beyond this one we think we experience, that is beyond the constructs of the mind, and some nirvana-like state is the real, non-illusory or whatnot, and this individuation we feel is illusory.

Just curious, what do you see as a counterfactual to this view, and why wouldn't it be right? Why couldn't there be simply individuation without the unity that you posit? In a trivial way, we can say by way of empirical studies that the world is fundamentally unified in that it matter and energy particles that came from a singularity right before the big bang. But of course, that is not what you mean either.

You were the one buttering the colloquial term ‘change’ not me. Everything we know of remains similar enough to call it the same. Nothing remains the same for humans because everything is subject entropy.

I think you are going a step beyond this and saying that there is a greater existence beyond this is beyond the constructs of the mind, and some nirvana-like state is the real, non-illusory or whatnot, and this individuation we feel is illusory. — schopenhauer1

That's the thrust of Watts' book, yes.

That's the thrust of Watts' book, yes. — Wayfarer

But the next part?

Just curious, what do you see as a counterfactual to this view, and why wouldn't it be right? Why couldn't there be simply individuation without the unity that you posit? In a trivial way, we can say by way of empirical studies that the world is fundamentally unified in that it matter and energy particles that came from a singularity right before the big bang. But of course, that is not what you mean either. — schopenhauer1

Edited a post above with second paragraph for clarification:
https://thephilosophyforum.com/discussion/comment/862509

Your view seems consistent with "origin essentialism": "biological individuals have their biological origins essentially." This is discussed in this SEP article. I don't disagree that our origins are necessary to being who we are, I just don't think it entails a sufficiently complete concept of identity. IMO, when you start digging into it, the concept of identity gets murky.

Two polar opposite positions highlight this:
1) haeccity (the notion of a "bare identity", entailing any particular identity could have been instantiated in practically anything. Your identity could have been instantiated in the body of your parent or child, or in a goat - and possibly in a rock.
2) hyperessentialism - the notion that 100% of our properties are essential to being who we are.

Both seem defensible concepts, but most aren't willing to accept one of the extreme.

I just don't think it entails a sufficiently complete concept of identity. — Relativist

And hence why I also say that it is necessary, just not sufficient...

When we think of ourselves as experiencing something, don't we generally think that what we experience is other than ourselves? — Janus

Well yes, but our selves are also experiences. And then consider that experiebces are going on in our heads as part of the goings on of a physical system which one might consider to be their self. So its interesting to see where the dividing lines are. Thinking about this, it seems that my experience of self is just a model of my body interacting, exercising its agency with its environment. Even though, given a thought experiment of removing my brain from my body, I wouldn't necessarily identify myself with my body.

You can lose parts of your body that are not critical to your survival and still be a living, experiencing body. — Janus

Yes, no doubt.

However, if you lose your eyes or lose your hearing you will not experience in those domains. A mere population of cells does not necessarily experience anything like you as an organism consisting of a self-regulating population of specialized cells does — Janus

I'm not sure I understand what you are saying here.

Roughly speaking the boundary of your being is your skin; it is natural enough to think of whatever is sensed within that boundary as part of oneself and whatever is sensed outside of that boundary as other. — Janus

There's lots of counterexamples to this kind of thing I think, such as the thought experiment of a brain transplant or something. At the same time, your body is itself full of living systems with their own boundaries. It is ofcourse natural to think that way, but I am skeptical that it is like an objective fact of the matter. *We might also characterize ourselves as parts of broader social and ecosystems, parts of a China brain perhaps even. There is also people who even propose extended mind theses about how our environment is an important part of cognition.

I would say your dead body is the dead you, which is very different than the living you, because it is no longer capable of internal self-regulation or of experiencing anything at all, either internal or external to it. It has become like any non-living object, but every particular non-living object is still thought to have a unique identity. — Janus

Yes, it seems complicated. There are a few different ways I could distinguish the concept of self here.

Edited: Minor addition * ... *

So you also bring up an idea that is along the same lines as Graham Harman who had a notion that objects are often "overmined" or "undermined". That is to say, often it is bypassed by being reduced to its parts or overmined for any relation whatsoever in the universe or at least, tangentially related to it. From Wiki:

"Object-oriented thought holds that there are two principal strategies for devaluing the philosophical import of objects.[18] First, one can undermine objects by claiming that they are an effect or manifestation of a deeper, underlying substance or force.[19] Second, one can "overmine" objects by either an idealism which holds that there is nothing beneath what appears in the mind or, as in social constructionism, by positing no independent reality outside of language, discourse or power.[20][21] Object-oriented philosophy fundamentally rejects both undermining and "overmining", since both approaches hand-wave objects away by attributing their existence to other, more fundamental elements of reality.[22]

In a 2013 paper, Graham Harman also discussed the concept of duomining.[23] Borrowing the word from computing science, Harman uses "duomining" to refer to philosophical or ontological approaches that both undermine and overmine objects at the same time. Harman asserts that Quentin Meillassoux's ontology is based on "a classic duomining position", since "he holds that the primary qualities of things are those which can be mathematized and denies that he is a Pythagorean, insisting that numbers do not exhaust the world but simply point to sort of "dead matter" whose exact metaphysical status is never clarified".[24]" — Wiki Article

Thanks for the interesting article, but I don't see a direct relation to the notion of individual identity, and it persistence over time. The issues here are not valuation, but how to precisely define what constitutes a persisting identity. I lean toward hyperessentialism and perdurance, and I don't think these conflict with valuations of objects.

Thanks for the interesting article, but I don't see a direct relation to the notion of individual identity, and it persistence over time. The issues here are not valuation, but how to precisely define what constitutes a persisting identity. I lean toward hyperessentialism and perdurance, and I don't think these conflict with valuations of objects. — Relativist

You seemed to hold the the opposite, negating its "perdurance" and essence over time.

Either way, there has to be "something" whereby it is differentiated form another thing. That is to say, whereby we can talk about that entity being an individual that is its own thing, and not simply a part of something else. Another set of gametes is not transposable. Hence, a second before or after would have been another person.

You seemed to hold the the opposite, negating its "perdurance" and essence over time. — schopenhauer1

Perdurance entails an object having "temporal parts". So there's a unique Schopenhauer1 at each point in time of your existence. The individual parts are linked through a causal chain. In gross terms: Schopenhauer1@Monday causes Schopenhauer1@Tuesday which causes Schopenhauer1@Wednesday...

The temporal parts aren't strictly identical to each other because the history builds over time (thus accounting for your changes over time), but collectively- the entire temporal, causal chain precisely defines the "something".

Identity of indiscernibles applies to each object at time t: all the properties the object has at time t are essential to being that object at time t. It also applies to the entire chain: only one individual can possibly correspond to the set of all those temporal parts.

The alternative to perdurance is endurance, and this is what I've criticized, because it leaves vague as to what constitutes personal identity and what is actually persisting over time.

The temporal parts aren't strictly identical to each other because the history builds over time (thus accounting for your changes over time), but collectively- the entire temporal, causal chain precisely defines the "something".

Identity of indiscernibles applies to each object at time t: all the properties the object has at time t are essential to being that object at time t. It also applies to the entire chain: only one individual can possibly correspond to the set of all those temporal parts. — Relativist

So even if I was to agree with this (which I don't think I do), the whole course of the causal-temporal chain starts somewhere. It doesn't start at the Big Bang. It doesn't start at your grandfather's birth. It started at the point when there was the set of possibilities that is the YOU now reflecting back, was put into play. Without that set of gametes, whatever object 1, 2, 3.. is would not be YOU, but another set.

And it is this that does touch on the point of overmining. As to overreach beyond the physical components to simply all causal relations, is to miss an essential component to the sweep of this set of causal-temporal events, the one thing that makes this set of causal-temporal events differentiated from others.

I/m sorry, but I don't understand what you mean by "buttering" in this message. On the other hand, perhaps it isn't important.

not important. Autocorrect

the whole course of the causal-temporal chain starts somewhere. It doesn't start at the Big Bang. It doesn't start at your grandfather's birth. It started at the point when there was the set of possibilities that is the YOU now reflecting back, was put into play. Without that set of gametes, whatever object 1, 2, 3.. is would not be YOU, but another set. — schopenhauer1

This is consistent with perdurantism.

It doesn't dictate a mereology (identifying parts), or force one to overmine, overreach, or undervalue the parts. Those analyses can still be applied.

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 — Ludwig V

it would be a rather daunting task for most to come up to speed on what is understood about noncoding DNA these days. — wonderer1

Yup.

I think my beliefs about DNA still pretty much rule out necessity between the particular sequence and identity, though I recognize that there are possibly significant differences too. But my intuition is that reality is not so rigid.

In some sense my name rigidly picks me out, and it would be true that the particular me could not, under any circumstances, be made out of ice from the Thames. But that's the name, and not the unique and particular description of my genetic code at the time of my conception. And for that it seems that DNA doesn't behave in a necessary relationship to the name that picks me out: rigid designators aren't ruled by causal patterns, but rather are just how we use names.

So in a way I could say that the genotype is a necessary but not sufficient condition for any identity to form. If you tried to gestate a whale zygote in a human the process would likely not end in life (though there are mules, too...) -- there's something necessary about having DNA at all, but I'm not so sure that the specific sequence that a person possess has a necessary relationship to the rigid designator which picks out who a person is.

In some sense my name rigidly picks me out, and it would be true that the particular me could not, under any circumstances, be made out of ice from the Thames. But that's the name, and not the unique and particular description of my genetic code at the time of my conception. And for that it seems that DNA doesn't behave in a necessary relationship to the name that picks me out: rigid designators aren't ruled by causal patterns, but rather are just how we use names. — Moliere

I know you’re trying to get some sort of rigid designation to work out here with your conception, but “what” object is the rigid designator rigidly designated with? You might be tempted to say that it can be anything or it’s functional, but there are certain physical substances that differentiate one object from all the other objects, there is a point at which an object could no longer be that object. There is a point when water is not water for example (it’s not H20). With natural kinds, for example, it is not simply that an object is dubbed in a causal chain, but also that it is made of that particular substance.

I know you’re trying to get some sort of rigid designation to work out here with your conception, but “what” object is the rigid designator rigidly designated with? You might be tempted to say that it can be anything or it’s functional, but there are certain physical substances that differentiate one object from all the other objects, there is a point at which am object could no longer be that object. There is a point when water is not water for example (it’s not H20). — schopenhauer1

I'd pick up the existential or phenomenological angle for identity. Somehow what's significant to us, what we care about, isn't the same as the list of facts of our past, though perhaps the facts one would consult in making a case for an existential identity is a subset of the entire set of every fact of our past. Existential identity comes from caring -- and insofar that the imagined scenario still results in a person caring in pretty much the same way then we can say they are the same even if some details differ.

Water is a bit different from identity because we can speak of a chemical's identity, but I don't think that's an existential identity like I allude to above. But I think I'd say that if water in Bizarro-world was primarily comprised of H3O and still was the stuff we drink when thirsty and more or less did all the same things which water does then I'd say it's the same stuff, even though in Bizarro-world the description differs -- but this wouldn't be on the basis of it caring. I think at a certain level "water" is such a clearly human interest that it's strange to think that this interest must have a corresponding descriptive correlate to it. Rather I think we're really interested in water because it's connected to our being alive, and so we investigate water and see what it is we can see about it. Here our name is much more in a functional space -- it's what it does for us rather than what we've come to describe it as which we're picking out.

Water is a bit different from identity because we can speak of a chemical's identity, but I don't think that's an existential identity like I allude to above. But I think I'd say that if water in Bizarro-world was primarily comprised of H3O and still was the stuff we drink when thirsty and more or less did all the same things which water does then I'd say it's the same stuff, even though in Bizarro-world the description differs -- but this wouldn't be on the basis of it caring. I think at a certain level "water" is such a clearly human interest that it's strange to think that this interest must have a corresponding descriptive correlate to it. Rather I think we're really interested in water because it's connected to our being alive, and so we investigate water and see what it is we can see about it. Here our name is much more in a functional space -- it's what it does for us rather than what we've come to describe it as which we're picking out. — Moliere

Here is an interesting passage from Wiki on rigid designators:

One puzzling consequence of Kripke semantics is that identities involving rigid designators are necessary. If water is H2O, then water is necessarily H2O. Since the terms 'water' and 'H2O' pick out the same object in every possible world, there is no possible world in which 'water' picks out something different from 'H2O'. Therefore, water is necessarily H2O. It is possible, of course, that we are mistaken about the chemical composition of water, but that does not affect the necessity of identities. What is not being claimed is that water is necessarily H2O, but conditionally, if water is H2O (though we may not know this, it does not change the fact if it is true), then water is necessarily H2O. — Wiki Article

So, I think I am in alignment with this, but with some additions. YOU is rigidly designated with the specific set of gametes for you to be you and not something else. This is true in all possible worlds. There is no world in which a different set of gametes would be you. That is all my claim is saying. If I was making a claim that those set of gametes are necessary and sufficient, then you can say that I am missing some things. Indeed, personhood can be quite existential in terms of how we identify things. However, we cannot lose sight of the necessary components that have to be in place for you to have been you and not something else.

This leads then to the idea of overmining and undermining. I can conceive of an argument whereby the interlocutor then states, "Well, why stop at the gametes? Why not your parents, the temperature in the room when you were conceived, the millisecond decision before or after? Those relations are also part of you!" And here is where Harman's notion of overmining becomes useful. We overlook a specific object to see all relations that could be connected to it. However, what makes that object, the object, needs to be understood. Now, Harman might also agree with you, that the necessary components can never be fully known, as they are "hidden" behind their causal influences. I can agree with even this, yet still insist that a well-known necessary aspect of what makes a person THIS person (and not something else) is the causal-temporal point at which the two gamete components combined.

Water is a kind, not an individual. The logic is a bit different. A closer example would be the Lectern used in Identity and Necessity. There i tis used with the demonstrative: this lectern. Kripke chose not to use that example in Naming and Necessity. But I wonder if the lack of clarity here is what led Kripke to drop the example.

The upshot in Identity and Necessity seems to be that while this person could not have had a different genetics, schopenhauer1 might have.

Water is a kind, not an individual. The logic is a bit different. A closer example would be the Lectern used in Identity and Necessity. There i tis used with the demonstrative: this lectern. Kripke chose not to use that example in Naming and Necessity. But I wonder if the lack of clarity here is what led Kripke to drop the example. — Banno

So this always bothered me.. Why would a kind be different than an individual in terms of substance that it is identified with? I will try to answer this in my own way that makes sense to me...

Where a kind is JUST identified with a substance, an individual is a combination of substance (this set of X matter/form/properties), AND a causal-temporally instantiated point in origin. At THIS point, this individual came into being with that X matter/form/properties. So it is actually combining the substance and causality approach to necessity.

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. — Ludwig V

Really what I meant was that the criteria for establishing identity, in the sense of being able to recognize any entity, are physical. I agree with you that identity is mostly understood in social terms, but I think that is a different issue.

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. — Ludwig V

I agree that the current understanding in genetics is that DNA can be expressed in different ways depending on environmental factors. It is thought that the way DNA is expressed determines, along with environmental conditions, all the forms of all the basic structures of our bodies, so it is not currently thought that everything is down to DNA in any absolutely rigid sense.

So, I would not say that DNA is the essence of what we are at all.

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. — Ludwig V

Well, no two leaves can be absolutely identical just because they inhabit different places if nothing else. I know a couple pairs of identical twins, and I can tell the difference between them just by examining their faces. Also I believe that the current understanding is that even identical twins do not have absolutely identical genotypes, Whether we could ever find any two natural objects of the senses, whether biological or not, which were physically indistinguishable, is an empirical question I agree.

So, I think I am in alignment with this, but with some additions. — schopenhauer1

I've always thought that some modifications were necessary. For example, there are two different kinds of water - heavy and light. Wikipedia tells me that "Ice exhibits at least eighteen phases (packing geometries), depending on temperature and pressure". (See Wkikipedia - Ice. These differences are associated with different behaviours of the material. We call both kinds water and all eighteen kinds ice - (though maybe those differences are not relevant - who would decide?). "Water is H20" and "Ice is H20" could politely be called an over-simplification. It's true that for some purposes, the differences don't matter, but for other purposes, they might. How does Kripke's argument cope with this?

It is possible, of course, that we are mistaken about the chemical composition of water, but that does not affect the necessity of identities. — Wiki Article

Well, even if we are right, in all the centuries before H2O was known, we didn't know what water is. How on earth did we manage to identify it? Luck?

The upshot in Identity and Necessity seems to be that while this person could not have had a different genetics, schopenhauer1 might have. — Banno

I think you are on the right track. But you are missing out the complexity of people. The unique identifier is surely "I", which does inescapably refer to the speaker (if used correctly). Admittedly, understanding "I" requires an understanding of "you" and the third person as well. Our names are useful as well, once we have learned them and learned how to respond to them. (You will understand that this is only a gesture for the much longer account that would be necessary to even approach accuracy.)

So, I would not say that DNA is the essence of what we are at all. — Janus

And I would agree with you.

Whether we could ever find any two natural objects of the senses, whether biological or not, which were physically indistinguishable, is an empirical question I agree. — Janus

Yes. But you inadvertently run into the oddity about the Identity of Indiscernibles. If you know you have two objects in front of you, you know they are not identical in all respects. The only way this problem could arise would be if you knew about two different appearances of the same object, which may not be both in front of you at the same time. We know how to cope with that in practice, but I'm not sure that logic does.