I thought it may be good to collect all my answers for the very useful “Ask a Philosopher” web site, coordinated by Geoffrey Klempner (if you are a professional philosopher and wish to lend a bit of your time to the initiative, contact Geoffrey directly). Here they are, in reverse chronological order (more recent first):

Where does theology end and philosophy begin? (13 August 2015)

I recently saw (YouTube) a very interesting discussion between Lawrence Krauss, Daniel Dennett and Massimo Pigliucci on the limits of science. One point that was not discussed adequately was that science sometimes turns to philosophers to help formulate the right questions. Dr. Krauss agreed apparently only if the physicist or other scientist runs out of questions to explore. I feel that the philosophy of science should play a larger role, but it intrigues me that scientists do turn to philosopher to formulate the right question. That is, how does one know that they’re asking the wrong question? Is there a method for evaluating such, and for formulating the right question? (17 July 2015)

Do philosophers agree on the nature of philosophy? (9 June 2015)

Is it possible to add into a naturalistic philosophy (naturalism) the existence of immaterial things? And, Is it possible that, though God did not exist, could immaterial things exist? (21 April 2015)

Why do we exist? What is our purpose? What happens after death? (17 February 2015)

How different might the laws of nature have been (in some other logically possible but nomologically impossible world)? Are there any limits? (21 January 2015)

For the philosopher, ‘because God said so’ is an unsatisfactory answer to the question ‘why is act X moral (or immoral)?’ Why? (25 November 2014)

‘A philosopher’s words are empty if they do not heal the suffering of mankind. For just as medicine is useless if it does not remove sickness from the body, so philosophy is useless if it does not remove suffering from the soul.’ (Epicurus). Agree, or disagree? (11 November 2014)

Existentialism and Stoicism are two well known philosophies of life. Are there any others you can think of? What makes a philosophy ‘practical’? (24 October 2014)

What is love? Have philosophers anything useful to add to Plato’s discussion of this question in the ‘Symposium’? (8 October 2014)

Today, we think that slavery is wrong and barbaric although once it was considered perfectly acceptable. Is it possible that in the future something we think is OK now will be judged in the same way? Any examples you can think of? (20 September 2014)

When we carry out a thought experiment, we can’t test the underlying philosophical hypothesis with any empirical data. So, besides logical flaws, what are the criteria for evaluating a philosophical hypothesis? And how can we benefit from thought experiments in our daily lives? (20 September 2014)

Is it acceptable in today’s post-postmodern society to lack a passion; to not be passionate? (2 September 2014)

Give three examples of how academic philosophy is useful in the contemporary world. (31 July 2014)

Is there free will? (31 July 2014)

Do philosophers still believe in the analytic-synthetic distinction? Did Quine in his attack on the analytic-synthetic distinction go too far or did he get it about right? (15 July 2015)

What are the various ways in which one could go about trying to demarcate science from pseudoscience? (9 June 2014)

What is holism? (9 June 2014)

What is relevant data that supports the inferences about “Do we use 10 per cent of our brain?” (9 June 2014)

If the universe was created in a Big Bang, before light, matter, and time; if there was no time how can there be a before? If there is no matter how can any reactions, chemical or physical or other, occur? It is impossible to make something with nothing. Is our universe just one of many, in a cycle created out of the death of another? Do you think the Big Bang was part of another cosmic event, i.e. the creation or death of other unknown universe(s)? (9 June 2014)

Please tell me, are objectivity, rationality and universality necessary requirements for all philosophical truths? Are they even possible? (9 June 2014)

Hi DM,

Yes, that’s exactly why a “zebra” interpretation of QM (aka “hidden variables”) won’t work, and why QM superposition is weirder, and thus not in accord with usual classical logic.

Out of interest, how do you see causality operating in the MUH? In my “naive” view, I’d see Thing A bumping in to Thing B and thus causing a change to Thing B. Would you go for a timeless, bird’s eye view of things?

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Philip,

“For (only, perhaps) the mathematical physicalists (if I am allowed to represent them), it’s (a subset of) what exists or could exist in some (conventional or unconventional, but still physical) computer”

Right, though I’m pretty sure that’s not what Tegmark means.

Coel,

“We have frameworks such as “Euclidean geometry” and “Newtonian gravity”. Both have axioms”

You insist in treating math and logic as if they were empirical sciences. They are not. There is a reason why we talk about “axioms” in one case and “assumptions” in the other. They share similarities, but they are also very different.

“If you adopt a mathematical or logic system, you can indeed make deductions from those axioms. But you can never prove that you have reasoned correctly, which follows from Godel’s demonstration that you can never prove that your reasoning within that system is self consistent”

I think you are taking Godel’s theorems to be more sweeping than they actually are.

“If you then want to adopt some other superset-system, to then demonstrate that your reasoning was self consistent, you then can’t demonstrate that your superset-system is self-consistent”

Not a super-set, but a partially different set. Look, Godel didn’t show that mathematicians don’t know shit, he only demonstrated (logically, by the way, not empirically!) that there are limits even in mathematics.

“Thus, logic itself can prove nothing.”

What???

“The only validation is then that it works, in the sense that it matches empirical behavior.”

No, sorry. There are countless conclusions in both logic and math that are not and cannot be validated empirically (because they don’t refer to the empirical world) and yet no logician or mathematician in his right mind doubts that they are true.

DM,

“Again, I’m not really a Tegmark acolyte”

With all due respect, you seem to be dismissing a bit too cavalierly the work of someone who has a lot of expertise in that field, and has probably put a lot more efforts in that hypothesis than you have, considering that you have a day job.

“I think you can continue ad infinitum asking what does it *mean* to say X, and it’s the question itself that I find relatively meaningless. What would an answer even look like?”

It would look like an ontological account. For instance, when I say that the planet Mars exists I mean to say that there is a physical object so-and-so constituted that is locatable by patio-temporal coordinates, and so forth.

“they are not physically real at all”

Then they are not real period.

“I am just another mathematical object”

I know you think that, but I think that position is, shall we say, highly problematic, as you know.

“Sherlock Holmes cannot be said to exist or not exist, because, as a non-mathematical object the term is just too fuzzy”

I would remind you that for Tegmark *everything* is a mathematical object.

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“I’m pretty sure that’s not what Tegmark means.”

Of course that’s why

mathematical physicalism(“removing the last vestiges of Platonism from mathematics” — László E. Szabó) isanti-Tergmark(who calls his MUH “Platonism on steroids”).LikeLike

ant-Tegmark(correction)Also accepting that “There are countless conclusions in both logic and math that are not and cannot be validated empirically (because they don’t refer to the empirical world)” depends on whether one is a mathematical Platonist vs. a mathematical physicalist or (strict) constructivist.

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Still, at it, eh? My remark looks like a lost pedestrian at rush hour. Carry on, gentleman. 🙂

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Hi Coel,

> QM superposition is weirder, and thus not in accord with usual classical logic.

Yes, it’s weird, but the idea that it contradicts logic just doesn’t work. “This electron is in a superposition of spin up and spin down” is not a contradiction in terms. The state is the superposition, not the measurement, so there is no contradiction.

> In my “naive” view, I’d see Thing A bumping in to Thing B and thus causing a change to Thing B. Would you go for a timeless, bird’s eye view of things?

I can hold both views at the same time, because they are in harmony with each other as far as I can see. You can take a timeless view of a work of fiction, but that doesn’t mean that certain events within the narrative are not caused by others. Or in cellular automata, you could take the evolution of the whole thing as a timeless mathematical structure, but that doesn’t preclude saying that this glider was annihilated because it collided with that one.

Massimo,

I never thought *you* would be admonishing *me* for not taking Tegmark seriously enough!

When I say I am not a Tegmark acolyte, that doesn’t mean I’m dismissing him. I take him far more seriously than most here. But just because I go along with his ideas for the most part does not bind me to agree with everything he says or the way he says it. And just because I have a second hand account of him supposedly conceding some point in a conference a while ago doesn’t help me understand what the philosophical objection is supposed to be, because I don’t see what the problem is with my answer (a mathematical object is just something that can be rigourously well-defined — “without baggage” as Tegmark would say)..

> Then they are not real period.

What is real depends on what you mean by real. In physicalist language what you say is true. In Platonist language it is not.

> when I say that the planet Mars exists I mean to say that there is a physical object so-and-so constituted that is locatable by patio-temporal coordinates, and so forth.

OK, so when I say the circle exists I mean it is well defined and has objective properties that are open to anyone to explore. Does that satisfy you?

> I would remind you that for Tegmark *everything* is a mathematical object.

And I would agree. Everything that exists is a mathematical object. But we can’t say whether Sherlock Holmes exists or not because the concept is too fuzzy to even figure out what it is we are talking about. The string of characters “Sherlock Holmes” exists and is a mathematical object. There is a universe somewhere where a chap calling himself Sherlock Holmes solves crime in a place identical to Victorian London, and he exists and is a mathematical object. Each Sherlock Holmes novel is a string of characters and so a mathematical object.There are so many ways to interpret the question that it is impossible to answer until terms are sufficiently clarified, and they are only sufficiently clarified when you end up with a mathematical object, and once you have done that then you have defined an object that exists.

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Hi Coel,

“Yes!”

So that statement says that a superposition is impossible and also the case.

So you are saying that it is impossible for an electron to be in a superposition?

Remember, classical logic says nothing at all about whether that is possible or impossible.

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However, different physicists phrase it differently. Some say “There is a such-and-such probability that, when observed, the electron will be in state spin-up and a such-and-such probability that, when observed, it will be in state spin-down”, in which case neither side of the conjunction is true.

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Lots of interesting debates here! I’m not sure I have much to say on the quantum logic discussion, but I had a couple thoughts on OSR.

Namely, I don’t think OSR and MUH are quite the same. As far as I understand it, OSR is primarily concerned with “structure” in some sense being ontologically more fundamental than strongly individuated, spatiotemporal objects with extensional relation, motivated by a combination of the theory-change, underdetermination etc. concerns that motivate epistemic structural realism with considerations about the ontology of modern physics, particularly QM.

For the most part, the OSR advocates seem to either say something like (to a first approximation) “objects exist but supervene on structure” (I’m thinking James Ladyman here) or “objects exist, but are not individuals” (Steven French says something like this), which they do by having multiple objects (x, y) but without identity relations (e.g. x=y is not defined).

OSR advocates do seem to often take the view that natural language is often misleading in these contexts and that mathematics is the best language to talk about such structure (Ladyman and Ross say something to the effect that it’s unlikely we can say very much “true or interesting” about such structure in natural language in Every Thing Must Go, if I remember correctly), and also draw heavily on group theory. There also is arguably a natural alliance with ante re structuralism in the philosophy of mathematics.

But whether the structure of the world is ontologically “mathematical” doesn’t seem to be the primary concern. In contrast, if I understand him, Tegmark seems to emphasize the Platonistic aspect of his views; the world literally is a distinctly

mathematicalstructure, an ensemble of all possible mathematical substructures. I might very well be wrong in my understanding of Tegmark’s views in particular, but it seems to me that at best the MUH could be considered a particular, particularly eccentric variety of OSR, and not identical with OSR in general.I want to just leave off with a quibble on the interpretation of QM.

DM,

“…which would probably fall afoul of Bell’s theorem due to having hidden variables.”

I’m not a physicist or philosopher of physics, but from what I’ve read in the foundations of QM/philosophy of physics literature, it seems that Bell’s theorem implies that you can’t have

nonlocalhidden variables theories, not that you can’t have hidden variables, and that locality is actually the big problem. This also seems to be how Bell himself interpreted the result. Tim Maudlin talks about this a lot, e.g. in Quantum Non-Locality and Relativity.Certainly there are other grounds on which people can and do oppose hidden-variables, such as the difficulty extending pilot-wave theories beyond basic QM, being physically unmotivated, and stuff like the Kochen-Specker theorem, but it’s certainly not uncontroversial one way or the other from what I as a non-expert can tell.

I’ll leave off with my own view of OSR, namely that I’m agnostic about it. I’m certainly very attracted to aspects of the program, in particular the empirical opposition to stuff like the Humean supervenience of analytic metaphysics, and the sensitivity to issues of modeling, partial truth, indirect representation etc. but I’m hardly sold on the whole thing.

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Forgive me, I meant

localhidden-variables theories in my discussion of Bell’s theorem. I really need to get better at proofreading these posts!LikeLike

For hidden variables, there are retrocausal models as well:

It is well-known that Bell’s Theorem and other No Hidden Variable theorems have a “retrocausal loophole”, because they assume that the values of pre-existing hidden variables are independent of future measurement settings.Huw Price, Ken Wharton – arxiv.org/abs/1307.7744

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A few of the above comments reminded me of a paper by Diderik Batens, who works on adaptive logics:

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Hi Robin,

It is impossible under classical logic (impossible under LNC) but is “also the case” in that it seems to be what really happens.

Hi DM,

It is not a contradiction in terms, but it is a contradiction of LNC.

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Hi Christian Gilberto,

I’m still not convinced that there is much of a difference between OSR and MUH. Your attempts to explain the difference come across to me like a difference only in the language used to express pretty similar ideas. Tegmark says the world is mathematics. Ladyman says the world is structure. To me, structure devoid of baggage or physicality or what have is just another way of saying what mathematics is.

I identify with the MUH because for me at least it is a much clearer way of putting it.

> it seems that Bell’s theorem implies that you can’t have nonlocal hidden variables theories

Of course you’re right, but it’s hard to see how my zebra analogy would be nonlocal! But yeah, in general, I’m perfectly happy to accept nonlocality as an expense of having hidden variables. This is how computer simulations would have to work.

Hi Coel,

> It is not a contradiction in terms, but it is a contradiction of LNC.

If it’s not a contradiction in terms, it is not a contradiction of LNC.

The superposition may or may not be a violation of LNC depending on how you model it. If you model having a state of spin up as A and having a state of spin down as ¬A, and you model a superposition as a conjunction, then yes, you end up with A AND ¬A, which violates LNC. But that’s a daft way of modelling it!

You could instead model spin up as A and spin down as B, and then you’d end up with A AND B, and that isn’t a contradiction. It’s still a daft way of modelling it because a superposition isn’t really a conjunction and we haven’t bothered to model amplitudes and so on, but it goes to prove the point that you have not proven that QM violates logic, because any attempt to show that the LNC has been violated depends on how you map your observations into statements in Boolean logic, and there are many ways to do that.

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The law of excluded middle: A rule for certain language games, but not one that all language games must necessarily follow.

– http://ndpr.nd.edu/news/38529-groundless-grounds-a-study-of-wittgenstein-and-heidegger/

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Hi DM,

Please, feel free to just call me Christian (although I am not one!)

On Bell’s theorem, certainly the nonlocality thing doesn’t really apply to your zebra example. I just wanted to point it out for the benefit of readers who may draw questionable conclusions from Bell.

As for OSR, I’m definitely willing to admit that MUH might be a variant of OSR, as I said, but OSR advocates don’t necessarily regard the structure of the world as lacking in “physicality.”

Ladyman’s version of OSR is probably closest to this, because he seems to deny that a strong distinction between concrete and abstract makes much sense based on current physics, so it’s wrong to ask for the distinctly “physical” structure of the world, but also wrong to talk about a distinctly mathematical structure. There simply are the various real patterns in the world, to use Dennett’s phrase as Ladyman and Ross do. This isn’t the same as saying that the world simply is a mathematical structure that is an ensemble of all possible mathematical structures.

But I think other forms of OSR explicitly draw a line between themselves and mathematical structure, and do claim that the “structure” of OSR is physical structure, or that at the very least the actual structure of the world can be distinguished from distinctly mathematical structure. Steven French argues for the former (“… the structure we are realists about is physical, not mathematical” (French 2014, pg. 141, also see chapter 8)) and Simon Saunders seems to think the latter if I remember the paper correctly (Saunders 2003).

Again, I want to make it clear that I think MUH could be thought of as a form of OSR, but I don’t think it’s coextensive with OSR, it’s just one variant, and I don’t think most forms of OSR simply collapse into Tegmark’s position.

Refs:

French, Steven. 2014.

The Structure of the World.Saunders, Simon. 2003. “Structural Realism Again.”

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Thanks Christian,

That makes a lot of sense and I’m happy to accept that.

But I would say that Tegmark might allow a distinction between the physical and the abstract, but that this distinction is subjective and dependent upon the perspective of the observer. What is physical for me is just what is in the same universe as I am. What is physical for an observer in a different mathematical object (universe) is abstract for me.

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Reblogged this on The Logical Place.

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