Consciousness cannot, whatever it is, be an illusion. The very notion of an illusion requires that there be something conscious that is being deluded. Any scientist, or anyone else, who says consciousness is an illusion is just misusing language.

Ah, okay, so you were just laying down a challenge to fill out the content of the term rather than stating point blank that the task could not be accomplished. That makes more sense.

A realist perspective is assumed because that is the way to construct a physical theory that is conceptually coherent.

A realist interpretation (quantum or otherwise) may be coherent, but this comment sounds like you are suggesting that anything other than a realist interpretation of physical theory (for instance, an instrumentalist one) would be incoherent. You would need to have a strong argument for that, independent, of course, of the bare (and ceded) fact that a realist interpretation of QM is coherent.

You're welcome - actually enjoyed dredging up memories of undergraduate mathematical logic (I was pretty good at it back in the day :wink: ). If you are confused about the numbers on the left, ask me a question about them - you might find that in framing the question you arrive at the answer yourself, but if not, I'll be happy to respond as best I can.

As to your second paragraph above, I'm not quite sure what you are asking me, sorry. If you have this premise :
(Ax)(Fx-->(Ey)(Gy & x=y))
You can derive
(Fa-->(Ey)(Gy & a=y))
by univeral elimination. Universal elimination allows you to substitute a constant term or name ('a') for a variable (in this case 'x') wherever that variable is bound by the universal quantifier. However, you cannot get from
(Fa-->(Ey)(Gy & a=y))
to
(Fa-->Ga & a=a))
by making the same substitution - no rule of inference I know of would warrant that step.

Could always be 133,000,000 pieces of drivel :wink:

I mean, people can't even agree on a mere definition of consciousness, let alone attempt to even speculate as to how - via what mechanism, or through what specific features - it might play a role in QM.

Sure, people might not be able to agree about a definition, but - unless you are a cranky eliminative materialist - there is something being disagreed about. "flufffwumps" - well, if I were to ask you what that was, you wouldn't even be able to point me to a literature of disagreement with which to get started. That's one difference between "consciousness" and "flufffwumps", and its a pretty significant one, and goes someway to saving the former from "meaninglessness" whilst leaving the latter as drivel.

I suppose the issue is this: if you are a realist about mental phenomena and a realist about physical phenomena, then - because we know from our own case that mental phenomena impinge on physical phenomena (e.g. what I want affects how I act in the world) - then there is some sort of correpondence between them to account for. One can avoid the issue by becoming a monist of some kind, but then one is no longer a realist about (at least) one of the realms, and possibly both. Donald Davidson, for example, tried to circumvent the issue monistically by saying that the world was made up of events, and the same events can be described using different vocabularly, mental or physical.

the argument for idealism could be accomplished just as well without referencing QM. — Moliere

Couldn't agree more - in fact I think I wrote somewhere at the beginning of this thread that idealism can be argued for entirely independently of QM. I've never seen a convincing argument of the form: if QM is true, idealism is true; QM is true, therefore idealism is true. Of course, if idealism is true, then there will presumably have to be some correct idealistic interpretation of QM to be given.

Allow be to be a little clearer. If one accepts that the wave function does collapse, then that it collapses in different ways in different circumstances is not in question: the question is why it collapses at all. An answer to that question begins with the idea that it collapses at the moment of conscious observation. If one is a proponent of this type of response you certainly owe an account of exactly how consciousness is involved in the process, but I still don't see why you believe it is meaningless noise right from the word go.
Anyway, there are QM theorists who believe that the wave function doesn't collapse in the first place.

I don't think QM has much to say on idealism, either way. — Moliere

Interpretations of QM have a lot to say about realism or idealism. Interpretations don't prove realism or idealism, of course, which is perhaps what you mean.

Does this entail some really cool philosophical implications? Definitely. But consciousness? Irrelevant noise. — StreetlightX

I'm not quite sure I follow you. I thought we were at least all agreed that one of the interesting questions QM invites is how to explain the so-called collapse of the wave function. One answer to that question, with a pedigree almost as old as QM itself, is that it collapses at the moment of conscious observation. Now, whatever role that gives consciousness in QM phenomena is another question, but I don't see why you think it is irrelevant noise. Are the only "cool" implications, as far as you are concerned, implications that ignore the possibilty that idealism might be true?

I'm not familiar with James's wedding ring analogy, but if the idea is that a physical description of the world is incomplete, and a subjective description actually goes on to fill in the gaps, then that still sounds a little like dualism. Frank Jackson at one time argued precisely that a complete physical description of the world would leave some facts undescribed - exactly the kind of facts that Nagel purports to exist, although argued for in a different way.

Mea culpa - apologies. My first comment was in fact directed at Kym, not you:

Herein lies a questionable assumption: That consciousness consists of "a single point of view". In reality internal experience is often quite conflicted, and we are in least two minds about everything from a menu preference to ideas of jurisprudence. Despite what we say, we often aren't even fully aware of how we feel about things until our emotional responses to events interact over time with our thoughts about them. Personally I don't hold much faith in Freud, but one thing he got right is that a mental persona consists of far more than a "single point of view". — Kym

Indeed, if you think there are two realms - the physical and the mental, the subjective and the objective, the inner and the outer - you are likely to face problems connecting the two together. First, if they are genuinely two distinct realms, then there must be things that exist in the one that will not correspond with things that exist in the other. You will also have the substantial task of filling out whatever you suppose the notion of correspondence actually is. You could deny the premise and adopt some kind of monism, which is what idealists (on the one hand) and eliminative materialists (on the other) do. But monisms face their own issues insofar as they have to at least account for the appearance (albeit illusory as far as monism is concerned) of their being at least two distinct realms.

For instance

Whatever may be the status of facts about what it is like to be a human
being, or a bat, or a Martian, these appear to be facts that embody a particular point of view. — Nagel

Churchland, of course, denies that there are any such facts.

Reread "What it is like to be a bat" - Nagel expressly draws a connection between subjectivity "the what it is like of experience" and having a point of view.

Regarding the part of your intial argument about points of view, I think Nagel's issue is not that there is just one point of view that a person takes for every event they witness that a scientific, third-person perspective leaves it out, but that there isat least one such point of view that the scientific perspective leaves out. That a single person might have multiple points of view of a single external event doesn't undermine Nagel's position - the issue is that there are these things called "points of view" and they have (or seem to have) no place in a scientific description of reality. They disappear from the scientific account (according to Nagel anyway) but are nonetheless things that do exist.

OK, Eros, first thing is that after taking a quick look at the way Forbes gives his answers, each line of your answers need to be structured in the folloing way:
a/p1, a/p2, .... ( N ) Statement l1, l2... L/P1 L/P2...
a/p1 on the left refers to the undischarged assumptions or premises that support the Statement. N) is just the line number of the argument. l1,l2 refer to the preceding line numbers of the argument you are giving that are being used to make the Statement, and L/P1... to the logical laws/statement types you are availing yourself of or making. If you don't follow that form in all your answers you will be penalized in your examination. Depending how strict your examiners are you may not get a single mark: "almost right" doesn't cut it in formal logic. Here is a simple example using propositional rather than predicate logic, but which will give you the basic idea:
1 (1) A → B Premise
2 (2) A→ C Premise
3 (3) A Assumption
1,3 (4) B 1,3 →E
2,3 (5) C 2,3 → E
1,2,3 (6) B & C 4,5 &I
1,2 (7) A → (B &C) 3,6 →I

So take a look at line (6) for instance. ON the right we see that we are using steps 4 and 5 of the argument plus the law of conjunction introduction. However, on the left we must list the assumptions or premises that allow us to make the statement, and here we are relying on the two premises we introduced and the assumption we made, lines 1, 2 and 3. At line (7) we use the implication introduction rule plus lines (3) and (6), but since the implication introduction rule tells us that in introducing an assumption as the antecedent of an implication, we discharge that assumption, on the left we now only need to list (1) and (2) as the steps of the argument we are still relying on (i.e. just our two initial premises).

Exactly the same principles apply to arguments in predicate logic, but you have extra/differently expressed laws of inference (universal and existential introduction/elimination for instance). You need to get into the habit of using precisely the same format in your answers.

I was a little confused as to why you had a separate line to state the contradictions you draw, but I see from Forbes's examples that this is how he has specified the Law of Non Contradiction - the system I used didn't require a separate line for stating the contradiction, you could simply refer back to the individual lines where the two contradictory statements were initially made. Anyway, that changes nothing, it's a matter of taste, but since you will be marked according to Forbes's system, you should continue to do as you are doing and express the contradiction explicitly on its own line (although I would use the actual symbol Forbes introduces for this, which looks like an elaborate "^" . If you want to do that in any subsequent posts, go ahead, I'll understand.)

As for getting from -(a=y) to a≠y, you need to look at exactly how Forbes deals formally with the law of identity, my guess is that he defines somewhere a rule that allows you to use the sign for non-identity (≠) as logically equivalent to the negation of an identity -(x=y). I don't have a copy of the book, and the excerpts I can get online are limited, so you are on your own there I'm afraid.

So, first off, skim the Forbes to see what he has to say about the law of identity, and then redo both your solutions in the format that Forbes requires. Then we can see if there are any other issues to address.

So, up to (8) everything is fine (except you forgot to close the brace at (2) - I know its nitpicking, but that's what formal logic requires). After (8) you should have:
(9) (Az)~Taz
(10) ~Taa
After that it depends what system of rules you are using, but when I learnt logic you would then do
(11) Taa & -Taa
(12) -Tba

The system I learnt also required that one list explicity at the end of each line which premises and assumptions were still "in play" in arriving at the line itself, which you are not doing above, but as Nagase says, it depends on the rules you've been given.

You discharge assumption (4) at step (6) by relying on assumption (5). You discharge assumption (8) at your step (10) but again you should be relying on (5) to do the discharging, you should not introduce (9). Since you now get your contradiction, and you only have assumption (5) left undischarged, you can discharge it by negating it. Does that help?

I'm not trying to substitute science with anything, let alone elementary school English. I'm a scientist by profession, and I like my pay packet. I don't even happen to believe that QM can be used to prove idealism. The only point I insist on, is that once you start making physical interpretations of QM equations, philosophical issues arise, and the great names of 20th century science share that opinion: Heisenberg, Bohr, Einstein, Schrodinger...... Take a moment to google "interpretation of quantum mechanics" to get a glimpse of what has gone on and is still going on.

Wow, that's expensive - I had no idea. I don't have a copy of that work, but did pick up a version of his The Case for Idealism secondhand for 20 pounds sterling a couple of years ago. Sounds like I should be looking to make a return on my investment! The Case for Idealism is a more technical academic work, but essentially makes the same points as the apparently more accessible A World for Us. If, after reading around the various reviews you are intrigued enough, we'll see if we can't find a cheaper way to get you a copy of one or the other, one way or another.

I think you are probably on to something that idealism tends to be regarded suspiciously because of its links with theism of one form or another. However, insofar as Berkeley is concerned, it's interesting to note that for him, at least, you could establish idealism independently of whether or not there was a God, and then use the fact that idealism is true to prove that there actually is a God. As for whether idealism can be cogently articulated, I believe it can - at least in its Berkeleian or phenomenalistic form (I cannot really speak to the Hegelian form, as I don't really understand Hegel). One recent academic philosopher who went against the grain and tried to do exactly that was John Foster. He is dead now, and as far as I know nobody has really picked up where he left off, but if you can get hold of a copy of his book A World for Us: The Case for Phenomenalistic Idealism, you might find exactly what you're looking for.

One difference to note is that Berkeley didn't believe in platonic ideas at all, he held (at least, it seems to me he held) a pretty extreme form of nominalism: the only things that existed for him were minds and their immediate contents, and even for God those immediate contents were particular datable locatable items, not timeless abstract forms.

My initial comment in this thread was to point out that quantum contextualism doesn't challenge mind-independent realism as Kastrup claims — Andrew

Quite right - QM may or may not challenge mind-independent realism, but Kastrup certainly hasn't given us any reasons for thinking so.

I certainly don't believe that secular beliefs are the reason why Kastrup is being criticized here. — Moliere

:up: I, for one, am criticising him on the basis that he is a bad philosopher.

Nothing in the data, or the formalisms, either. — StreetlightX

Nobody - well certainly not me in any case - is saying that the formal aspects of QM include reference to conscious observers. That's not the point. Take the Schrodinger wave equation, for instance - absolutely no explicit reference to a conscious observer at all. The solutions to that equation for a given system provide us values that the Schrodinger wave function can take for that system, but the philosophical issues (where there are very real distinctions between observation, measurement and interaction) begin when physical interpretations of those values are proposed. It's generally agreed that the wavefunction values generate probability distributions, but probability distributions of what? One response is along the lines "the probability of finding a particle to be at a particular location" and straight away you see a notion involving conscious activity being introduced (i.e. "finding").

From where do you derive your certainty concerning the meaning to be given to terms like "observation" and "measurement" in QM? Heisenberg and Bohr advocated for the position that those terms invovled consciousness in some way or form. Other scientists disagreed with them (I think Einstein believed that QM could be developed without the notion of an observer at all). As far as I am aware the debate is not settled, and Carlo Rovelli cannot settle it by simply defining away the problem by equating "observation" with "interaction".

I'm all for thinking outside academic boxes, and materialsim is very definitely one of those boxes. We have no disagreement there. I just think Kastrup does a disservice to the position he is arguing for by making "schoolboy" philosophical errors, and that he makes those errors is not a subjective opinion.

And in any case, idealism doesn't require support from the philosophically naive Kastrup, and it can be argued for entirely independently of any interpretative issues in QM.

At the risk of being accused of sophism:

The 'observer' in QM has a causal role: the physical set-up of the apparatus will cause, in a double-slit experiment, light to appear as either a wave or a particle

If the event caused is an appearance (or a disjunction of appearances) then we still seem to have "observation" in a more psychological sense imported into QM don't we?

I'm not sure that this is right - or at least it is part of the problem under discussion. Suppose we neutrally define "observer" as whatever takes measurements. Whilst physical apparatus might be used to take measurements, it is the experimenter him or her self that actually takes/records the measurements. At least that is a distinction that it is extremely natural to make. Rovelli saying that an observer can be a table lamp seems to be ignoring this distinction and thus stomping right over the fundamental metaphysical problems.

Perhaps I am being a little harsh, although I did also describe him as an excellent scientist. The problem scientists have when they venture into philosophy unprepared is that they make very basic errors, errors which undermine their whole point. Take, for instance, the following couple of paragraphs from the beginning of the paper Wayfarer provided the link to:

There have been attempts to preserve some form of realism by finding a subset of
physical properties whose values can be determined in a non-contextual manner under certain circumstances. The idea is then to claim that this subset isthe objective physical world. For instance, Philippe Grangier [Grangier, 2001], inspired by Einst
ein-Podolsky-Rosen’s view of what constitutes physical objectivity, contends that the qua
ntum state of a system, defined “by the values of a set of physical quantities, which can be predicted with certainty and measured repeatedly without perturbing in any way the system,” [Grangier, 2001: 1] is an objective physical entity.
The problem with this approach is highlighted by Grangier himself: the “defi
nition [of the quantum state] is inferred from observations which are made
at the macroscopic level” [Grangier, 2001: 2]. In other words, the supposedly physically
objective quantum state of a system depends on the a priori existence of a physically objective classical world surrounding the system. This begs the question of physical objectivity instead of rendering it viable under contextuality. Because “a quantum state ‘involving the environment’ cannot be consistently defined” [Grangier, 2001: 4], Grangier’s approach fails to reconcile contextuality with a supposedly physically objective world. — Kastrup

What's the fundamental philosophical mistake Kastrup is making? The point he is dealing with is the attempt to reconcile realism with contextuality (by which he seems to mean the alledged fact that in experimental realm of quantum mechanics, observation affects outcomes). Perhaps he is right that realism faces this challenge. However, that challenge is a very different challenge from attempting to prove that realism is true. Kastrup's claims about question begging would only undermine Grangier if Grangier were attempting to prove realism, not if he is simply trying to reconcile two apparently contradictory positions. When reconciling two positions you are perfectly entitled (in fact are probably obligated) to assume the truth of both positions and you do not have to argue non-circularly for either one of them.

Don't get me wrong, I'm no hardheaded realist, but it does no favours for idealism when its advocates make basic errors of this kind.

The existence of free will, and its compatibility or otherwise with causal determinism, is a philosophical mine field, which Kant also tried to negotiate in the Critique of Pure Reason. Some have argued that no moral notions make sense unless we have a very strong form of free will, and the fact that the universe and everything in it runs according to causal laws (even if those laws are stochastic) entails that we do not have that kind of free will. Therefore no moral notions make sense. Kant's basic thought about this, I think, was that arguments about causal determinism have bite for theoretical ('pure') reason, but morality is the domain of practical reason, so is untouched by any such concerns. Seems a little flimsy when stated so bluntly, and you should really read Kant for yourself as I may not be doing him justice.

Even Kant in the Critique of Pure Reason thought proofs of God were a conceit - he specifically argues that it is impossible to prove that God exists in that work. His basic argument was (and here I'm shamelessly copy/pasting from https://metaphysicsnow.com/2018/03/18/god/)

...the structure of Kant’s argument is very simple:

No argument for the existence of God will work unless the Ontological Argument works.
The Ontological Argument does not work.

Therefore, no argument for the existence of God will work.

Of course, Kant may not have been right about that.
As for intuitions of being, if "being" here is supposed to be something that comes before or transcends space and time themselves, then Kant is just going to deny that humans can have such any intuition because (at least as he was using the term "intuition") space and time are the very forms under which human beings can have any intuitions at all.

Perhaps I'm being a little harsh - although I did describe him as an excellent scientist. But even in the more reasonably argued artice Waferer talks about Kastrup makes a basic philosophical error:

There have been attempts to preserve some form of realism by finding a subset of
physical properties whose values can be determined in a non-contextual manner under certain circumstances. The idea is then to claim that this subset is the objective physical world. For instance, Philippe Grangier [Grangier, 2001], inspired by Einstein-Podolsky-Rosen’s view of what constitutes physical objectivity, contends that the quantum state of a system, defined by the values of a set of physical quantities, which can be predicted with certainty and measured repeatedly without perturbingin any way the system, is an objective physical entity.
The problem with this approach is highlighted by Grangier himself: the “definition [of
the quantum state] is inferred from observations which are made at the macroscopic level”. In other words, the supposedly physically objective quantum state of a system depends on the a priori existence of a physically objective classical world surroundingthe system. This begs the question of physical objectivity instead of rendering it viable under contextuality. Because “a quantum state‘involving the environment’ cannot be consistently defined” [Grangier, 2001: 4], Grangier’s approach fails to reconcile contextuality with a supposedly physically objective world

What's the philosophical error? The challenge Kastrup seems to think the realist must meet is to render realism a coherent position in the face of contextuality. Fine, but that is a very different challenge from proving that realism is true. The accusation of question begging Kastrup levels against Grangier would only undermine the attempt to do the latter, not the former. If your aim is to reconcile a position with another position you are perfectly entitled to assume both positions are true, you don't have to argue for or against either one of them.

Don't get me wrong, I'm no hardheaded realist, but sloppy reasoning does no favours for idealism.

Agreed. Although as far as I am concerned he is probably on the side of the angels, he is a very good example of an excellent scientist and execrable philosopher.

Which it clear doesn't :wink: OK, I thought maybe there was a known argument that takes deflationism as a premise and reaches realism as a conclusion by way of some more sophisticated chain of inference.

My point was that the grammar of the statement "John saw a red, round afterimage" doesn't imply that we are "treating afterimages as actual things with such features" (and that adverbialism doesn't avoid this by using the statement "John sensed redly and roundly"), just as the grammar of the statement "it is raining" doesn't imply that there's some thing which performs the activity of raining. The statements are just how we speak, nothing more.

I agree, to some extent at least. It's the adverbialist that puts the emphasis on logical form and I introduced the problem in an "adverbialist-friendly" manner. But as far as I'm concerned it's really the phenomenology that points to afterimages being objects of vision, and the adverbialist is ignoring the phenomenology.

I've never come across arguments that deflationism/disquotationalism supports realism rather than idealism (or anti-realism of any kind). What/who would be a good example of that kind of position?

If you want to argue for direct realism, indirect realism, idealism, or something else then that's fine, but to do so with reference to the allegedly 'competing' statements "John saw a red, round afterimage" and "John sensed redly and roundly" seems misplaced.

I completely agree - if you want to argue for idealism then you need to do a lot more work, and that's not what I'm doing here. The main idea I'm trying to explore in this thread is just that adverbialism does not provide realists with a means of diffusing the idealist's position, and that ultimately it is just a linguistic sleight of hand which leaves the main issue untouched. Wittgenstein's remark about "it is raining" was supposed to show that not every use of a pronoun requires that there be something referred to by that term, and comes (if I remember correctly) in the context of discussing what "I" refers to in statements like "I feel pain". He may (or may not) have been right about that, but I'm not sure what its relevance is to the idealist's position that "John saw an afterimage" and "John saw a football" are statements made true in exactly the same kind of way: i.e. by the existence of objects of vision. When we ask "what does 'it' refer to in "it is raining"?" it is indeed a strange question, one we would not naturally ask and to which no answer seems clear and perhaps none can be given, and to that extent the question may have no meaning. But "what is an afterimage?" is a question that makes perfect sense, which can be investigated and to which different answers can and continue to be given.