My token identity is maintained, despite the flux of my physical body, by the way I think and talk about myself (and the way others think and talk about me). I'm the same person that was alive 20 years ago because that's how I think and talk about myself. That's anti-realism. — Michael

For one thing, you are a very complex and unique structure. I don't see you as a token at all, and I doubt that "token identity" is a useful concept to apply to yourself.

For another -- since one of my (self-allocated) roles here is to popularize biology as the most important science of all -- let me add that your identity is also maintained biologically by your immune system. That provides an objective, structural underpinning and a sine qua non condition for your continued existence as a mental construct, able to maintain some sense of mental identity and stability. Without this biological ID maintenance system (i.e. your immune system), you would die very soon.

Interestingly, this system is strongly connected to your mental life: it is depressed when you are psychologically depressed for instance. So if you really believe that your life is not worth living, your immune system may stop (or reduce) defending and maintaining your biological integrity.

I guess what I am saying here is: reality is multilayered; there are many many levels and interconnections, which tend to be bulldozed by simplistic metaphysics, in particular the kind of naïvely materialist, reductionist metaphysics often inspired from classic physics. Biologists and biology-inspired philosophers know better than that. And one of the concepts that biology brings forth (as opposed to physics) is that notion of structure and the related notion of function.

These notions of structure and function are fundamental to the questions of identity that you are trying to explore. There's more to our sense of reality and identity than just the material composition of stuff: there is structure, shape, utility, behavior...

A recently dead corpse and a living man are identical when you just look at their material composition... Yet there are important differences between being dead and being alive.

it's not paraconsistent logic - which holds that A, ~A ⊨ B is not a valid inference; this is the view usually associated with anti-realism. — Banno

I believe this is where we diverge. Anti-realism isn't concerned with explosion as a logical matter, it (the middle-way anti-realism) is concerned with how all truths are known yet some truths are unknown (anti-realism plus non-omniscience) in a meaningful (non-incoherent/useful) way. I thought my quotes pointed strongly in the direction that paraconsistent logic is not, in and of itself, the issue, but the paradox:

Beall suggests that the knower gives us some independent evidence for thinking Kp∧¬Kp, for some p — “SEP on Fitch’s Paradox”

I am not sure how anti-realism plus denying explosion would solve the knower's paradox as a philosophical matter, it would just say let anti-realists say, "Yes, there is a contradiction, but you can't prove anything else as a result." If the anti-realist does not want to permit contradictions in the first place (How absurd!), non-explosion doesn't do the necessary work. I grant I could be missing a nuance.

Michael's claim regarding multiple truth values was addressed by Priest in the article when he discussed "value of" as a relation rather than a function. So yes, what Michael suggests is not classical logic, but it is a possibility accounted for in paraconsistent logics which leads me to think that paraconsistent logics reject the principle of bivalence in-so-far as it requires a proposition have only one truth value. This is distinct, I believe, from having a third truth value, i.e. paraconsistent logics are not necessarily multi-valued logics, cf. multivalued paraconsistent logics .

Anti-realism isn't concerned with explosion as a logical matter, it (the middle-way anti-realism) is concerned with how all truths are known yet some truths are unknown (anti-realism plus non-omniscience) in a meaningful (non-incoherent/useful) way. — Ennui Elucidator

There is no problem of omniscience. Using verificationism as an example, if one is omniscient then for every meaningful proposition p either p or ¬p has been verified. Verificationism doesn't argue that every p or ¬p has been verified. There are many classes of p where neither p nor ¬p have been verified.

I don't need to be a mathematical realist to claim to not know the square root of 123, and not knowing the square root of 123 shows me to not be omniscient.

Carnap's verificationism was a proposal for structuring the language of science to highlight public observation and avoid 'wearisome controversy.'

It's not a theory of meaning or truth. It's definitely not anti-realism.

This is more concerning Dummett's verificationism, not Carnap's.

On whose account of anti-realism? What is true that is unknown on their account and how does their account differ from realism?

Verificationists, as I said. Nothing unknown is true, because to be true is to be verified, but not all propositions have been verified, and so they don’t know everything.

It differs from realism because realism argues for unknown truths.

It differs from realism because realism argues for unknown truths. — Michael

Dummett style verificationism also allows us to talk about unknown truths. It just says it's meaningless to talk about truth regarding the unverifiable.

True. I guess I’m just going along with Banno’s account of verificationism here https://thephilosophyforum.com/discussion/comment/603899

In my view there's nothing naive about 'naive anti-realism', so it doesn't need moderation. So-called moderate anti-realism is either a generalized form of realism in disguise, else it is a contradiction in terms.

One is either a realist about a proposition P or one isn't. If one is an anti-realist about P, then to assert P is to know P, so an anti-realist cannot say P and ~Know P. This isn't a problem, provided the anti-realist gives an account of "false" assertions so as to eliminate the need for ~Know P, as i'll mention below.

Firstly, suppose a mathematician says "The Goldbach conjecture P might be provable in Peano Arithmetic, but we just don't know". What he means is something like " A well-formed formula named 'P' hasn't so far been obtained as the conclusion of a proof object of PA".

If the above example from classical logic is expressed by saying " P or ~P and ~Know P" then it should be understood that the sign "~" of logical negation indicates that "Know P" isn't a referring term because a proof-object of P doesn't presently exist. Consequently the proposition " P or ~P and ~Know P" can be deflated to "P or ~P" without loss of meaning, where "P or ~P" is trivially true as per the definition of PA. Also notice that "P or ~P" and "Know (P or ~P)" are identical propositions in referring to the axiom known as LOM.

Likewise, to take a non-mathematical example, consider this weekend's boxing match between Tyson Fury vs Deontay Wilder. To assert today, on Thursday the 7th October, that "Either Fury or Wilder will win, but nobody knows for certain" is merely to say "Fury or Wilder will win", which it should be noticed is a description of todays state of affairs, and not of a hypothetical future state of affairs that doesn't presently exist. Therefore, even if this weekend's fight ends in a draw, today's assertion should be seen to remain true, in so far as it is an accurate description of todays state of affairs.

My token identity is maintained, despite the flux of my physical body, by the way I think and talk about myself (and the way others think and talk about me). I'm the same person that was alive 20 years ago because that's how I think and talk about myself. That's anti-realism — Michael

How do you know that your memories and consciousness aren't also in flux? That you believe you have maintained a constant experience of your consciousness from childhood until today may or may not be objectively true, especially considering the many distractions and sleep states you've been in that have interrupted that consciousness. That is, it is no more a forced delusion for me to claim that I'm the same string of consciousness today than what I was since childhood as it is for me to say that I'm the same physical component today than what I was since childhood.

Whatever undefined thing that lingers in your brain that keeps your consciousness stable throughout life seems no more or less incorruptible and absolute than your DNA that keeps your corporeal composition stable.

It just seems like you've removed objective reality from the equation as the anchor for truth and replaced it with objective consciousness, but I don't see why the latter avoids the problems of the former.

But verificationism holds that p is true if and only if it has been verified. — Banno

If so, it's undercutting itself because that isn't verifiable.

It's both. Vague propositions often don't have a single truth value, precisely because they're vague. — Michael

A vague proposition that is so vague that it doesn't have a truth value isn't a proposition. A propositional statement is defined as a statement with a truth value that is either true or false. https://penandthepad.com/propositional-statement-6943651.html

If no statements, as you've argued, have single truth values, then no statements are propositional. That is the result of removing the truth component from the equation. If I say "The hat is green" and I cannot define what a hat is, what it is to exist, and what green is, then I've said nothing about the world and not asserted a propositional statement.

You mean this definition?

But verificationism holds that p is true if and only if it has been verified.

And it follows that everything that is true has been verified. — Banno

So Banno's verificationism says that everything that is true has been verified and you say that verificationism permits unknown truths. Please give an example of something that is verified true but is unknown. As of yet unverified propositions are necessarily not true according to Banno's account and, so far as I can tell, a not true thing is false on the typical account. So which P is unverified, true, and unknown to be true.

If so, it's undercutting itself because that isn't verifiable. — frank

Everytime I read "verification" on this thread I replace it mentally by "falsification". Works better I think.

So Banno's verificationism says that everything that is true has been verified and you say that verificationism permits unknown truths. — Ennui Elucidator

No I don’t. Verificationism doesn’t permit unknown truths. It permits unverified propositions.

No I don’t. Verificationism doesn’t permit unknown truths. It permits unverified propositions. — Michael

So why do you say that verificationism doesn't require omniscience? All truths are known.

So why do you say that verificationism doesn't require omniscience? All truths are known. — Ennui Elucidator

Because under verificationism that isn’t sufficient to be omniscient. Omniscience requires having verified every proposition or their negation.

A verificationist might not have verified the square root of 123. He doesn’t know the square root of 123 so he isn’t omniscient.

Because under verificationism that isn’t sufficient to be omniscient. Omniscience requires having verified every proposition or their negation. — Michael

You keep saying this. Who says that verificationism doesn't require omniscience? If omniscience is knowing every true thing and every true thing is known....

It is however the contrapositive of Theorem 5 that is usually referred to as the paradox:
(K Paradox)∀p(p→◊Kp)⊢∀p(p→Kp).

It tells us that if any truth can be known then it follows that every truth is in fact known. — SEP on Fitch

Fitch’s paradox of knowability (aka the knowability paradox or Church-Fitch Paradox) concerns any theory committed to the thesis that all truths are knowable. Historical examples of such theories arguably include Michael Dummett’s semantic antirealism (i.e., the view that any truth is verifiable)

If omniscience is knowing every true thing… . — Ennui Elucidator

Properly speaking it’s knowing the truth value of every proposition. In the case of verificationism that requires having verified every proposition (or their negative) which verificationists don’t claim to have done.

Yet again, if the verificationist hasn’t verified the square root of 123 then he isn’t omniscient. It’s that simple.

Here's a P that isn't verifiable:

Pressure=volume x temperature

It's not verifiable because we would have to have a time machine to cruise through reality and check that it works every time.

So you could insist that it's either true or false, but what does that mean considering that we can't check?

Yet again, if the verificationist hasn’t verified the square root of 123 then he isn’t omniscient. It’s that simple. — Michael

If the verificationist hasn't verified it, it isn't true. The nice thing about being omniscient is that knowing everything that is true (i.e. every proposition that has been verified) neatly discloses everything that is false (every proposition that hasn't). It isn't like I'm the person that said that Fitch's paradox of knowability is a problem for verificationists. This type of omniscience is precisely the naive anti-realism that is required when the middle way gets hoisted on Fitch's petard.

The operative concept of “knowability” remains elusive but is meant to fall somewhere between equating truth uninformatively with what God would know and equating truth naively with what humans actually know. Equating truth with what God would know does not improve intelligibility, and equating it with what humans actually know fails to appreciate the objectivity and discoverability of truth. ...

The great problem for the middle way is Fitch’s paradox. It is the proof that shows (in a normal modal logic augmented with the knowledge operator) that “all truths are knowable” entails “all truths are known”... — "SEP

:100:

Like any general law, it is unverifiable, which is why logical positivism failed and gave way to Popper's formulation of the falsifiability principle, not as a demarcation between propositions with meaning and those without, but between scientific and non-scientific theories. For Popper, non-falsifiable propositions are not necessarily without meaning, just without possibility of empirical testing and thus not part of 'science' proper (specifically when this proposition is also not part of a broader theory which makes some testable predictions).

If the verificationist hasn't verified it, it isn't true — Ennui Elucidator

Precisely.

knowing everything that is true (i.e. every proposition that has been verified) neatly discloses everything that is false (every proposition that hasn't). — Ennui Elucidator

Not having verified p isn’t the same as having verified not-p. You need to verify not-p for p to be false.

For Popper, non-falsifiable propositions are not necessarily without meaning, just without possibility of empirical testing and thus not part of 'science' proper (specifically when this proposition is also not part of a broader theory which makes some testable predictions — Olivier5

I posted a video to the shoutbox a while back that showed a few physicists talking about Popper. The consensus seemed to be that, with all due respect to Popper, they do what they want.

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. — Michael

Too big a jump - no, it's a conventional view of naming that has little to do with the substance of the ship.

...because we view it that way. — Michael

Same point. For your argument to work you will need to show that realists can't employ coventional views of naming. Cleary, they do.

Same for the last quote.

What you haven't done is show that realists cannot engage conventions in naming. If you can do that you would have an argument. So for example Searle is a realist who gives an extensive account of the conventional aspect of naming. You would need to show how he is in error.

I think you are working with a somewhat reduced notion of naive realism. Given that realism is the default possition amongst philosophers, something with more grunt is going to be needed.

It’s not just about conventions of naming. We’re questioning whether or not a token identity is maintained. We’re discussing the referent(s) of the name(s), not just the name(s).

Do “the Perseus” and “the Theseus” have the same referent?

A realist can't agree with this, as set out by you above; — Michael

Again, you haven't shown this. It is open to a realist to say that we can give the same name to different things, as well as to things that change over time.

Indeed, this is what they do.

Not having verified p isn’t the same as having verified not-p. You need to verify not-p for p to be false. — Michael

So you are abandoning the principle of bi-valance?

Also, I think you are about to engage in a dangerous game when you suggest that P can be true and ~P can be true because they are separate propositions. The tilda, which stands for "not", is a logical operator, not a feature of the proposition being negated (i.e. the tilda is the logical operator that means that the atomic or complex formula represented by P is not true).

Do “the Perseus” and the “the Theseus” have the same referent? — Michael

The answer is that it is up to us to choose.

Is that picture a duck or a rabbit? It's a picture that can be seen either way. Neither is obligatory.

Further, and more importantly in this case, it is a real picture.