# What is the name of the principle saying it is meaningless to talk/ask questions that can not be measured/tested?

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Watching quantum mechanics lectures and it was mentioned that it is pointless/meaningless to try to talk/question things that can not be tested/measured.

Is this a principle? And if so what is it's name?

Also does this apply to questions other than Quantum mechanics? E.g. does it make sense to ask if earth was the only object in universe if gravity would still exist? Although it seems intuitive to answer yes, yet it is something that can never be tested/verified. It seems almost as meaningless as to ask if the universe was only made of a unicorn would it have gravity?

As an analogy consider glottogony, at some point it was banned as it seemed to be an unanswerable problem. http://en.wikipedia.org/wiki/Origin_of_language

This post imported from StackExchange Physics at 2014-04-04 16:52 (UCT), posted by SE-user Arjang
retagged Apr 4, 2014

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This principle is called "positivism". But I prefer the term "logical positivism".

Positivism is a basic principle of thought--- it distinguishes questions which are meaningful and meaningless. It is not meaningful to ask "How does Argentinian property law taste?", it is not meaningful to ask "How many angels can dance on the head of a pin?", and it is not meaningful to ask "Wny is there something rather than nothing". These questions have the property that, whatever the answer, there is no consequence to our perception of the world, or to anything that we can measure. Such questions do not need an answer, because they are just words put together without meaning.

Philosophers do not accept positivism, because it moots many of their favorite questions. For example "how can we have free will in a deterministic universe?". This question, although superficially so clear, is positivistically meaningless, because there is no measurement which can be made upon a creature's decision making power which can in any way determine whether the underlying laws are deterministic or not. This question is moot, because if you define "free will" properly, it cannot possibly have anything to do with determinism. You can't figure out that quantum mechanics is not deterministic by introspection, because your introspection has nothing to do with the determinism of the underlying laws.

Similar jibberish:

• If the universe exists, doesn't it require a prime mover?
• Is ethics/mathematics defined independently of human beings, or do we produce it?
• If God is good, how come there is so much suffering in the world?

Basically, half the philosophy curriculum is brain-dead nonsense, and the rest requires massive restructuring to eliminate redundancies. Religion, when formulated positivistically, is not nonsense, and it is possible to formulate religion, including monotheistic religion, in positivist terms, only throwing away the metaphysics and keeping the meat of it.

Logical positivism is an early twentieth century tradition that combined the notion of scientific positivism with the new concept of a formal language, then being developed in Logic by Boole, Frege, Russell, Hilbert, and others. The logical positivists wished to get rid of the other annoyance of philosophy, the fact that we have to deal with imprecise natural language. The goal was to replace natural language with a formal language, in which all the terms of discourse are precisely defined. In this way, you would remove another huge branch of philosphy, namely that philosophy whose goal is to make sense of the various ambiguities in the writings of other philosphers.

The formal languages at the time were barely adequate for formalizing mathematics. It was a bold leap to assume that formal languages could encompass a large enough domain of discourse to approximate natural language. This leap was associated with a bunch of people who I am not going to name, because I haven't read any of them, because philosophy is so trivial compared to any real intellectual work, that you can reproduce any of the results of the non-mathematical philosophers for yourself by thinking for ten minutes.

Logical positivism moots a whole bunch of other philosophy, because it suggests that the right way to think of terms in a language is in terms of a reduction to a formal language, much like in mathematics. If you take the positivists seriously, most of the field of philosophy is pointless and stupid.

At first, philosophers celebrated the revolutionary ideas, and positivism was the ascendent philosophy until the 1950s. But with the emergence of horrific totalitarian states with scientific materialism as their religion, scientific materialism lost ground, and by the 1970s, it was killed off in the west.

### The positive influence of positivism

People think positivism equals quantum mechanics, because quantum mechanics was formulated strictly in positivist terms, using "observables". But it wasn't only in quantum mechanics that positivism was important:

• Fields: the notion of fields, which is so abstract, acquires meaning through positivism. How can you tell if a field is there? Put a charge there and see it move! This positivist formulation was important in making clear that a concept that seems so immaterial to many people at first glance is in fact real.
• Luminiferous ether: the ether lost its material characteristics one by one, and it was an act of positivism by Einstein to reject the ether completely, because it had become unobservable.
• Equivalence principle: In order to get from the fact that you can't observe gravity in a free-falling frame to the principle that gravity is a geometric force, Einstein made an act of positivism. If the effects of acceleration are indistinguishable from gravity, then gravity and acceleration must be the same thing in essence. This is a very predictive statement.
• String theory: String theory emerged from a positivistic question--- how can you make a measurement in a space-time that is not well defined at short distances? The answer was to speak about s-matrix states, and their scattering. In physics, the resulting S-matrix theory led to string theory, which is the only candidate for a theory of everything.
• Black hole interiors/holography: Within string theory, the rejection of the simultaneous existence of the interior and exterior (since each are observed by different observers) led to the fruitful principles of black-hole complementarity and holography as developed by Susskind.

There are also several cases where positivism was misapplied overzealously, and I think this clarified things:

• Quantum field theory is meaningless--- because it is difficult to imagine measuring a quantum field. In fact, the original paper of Bohr-Rosenfeld analyzed measurements of the quantum electric and magnetic field, and decided that it made sense to quantize them. the positivist's complaint was about ultra-short distances, and for those distances you need to deal with gravity anyway.
• Quarks don't exist--- it is impossible to isolate quarks. This is no better an argument than Mach's argument that atoms don't exist because he can't see them. If there are observable phenomena which are best explained using quarks, then quarks exist to the extent that they are included in the explanation. The real battle here was over quantum field theory, and the postivists were the folks doing the s-matrix theory.

Outside of physics, positivism is identified with this ridiculous claim:

• Interior experience doesn't exist--- since all we can measure are inputs and behavior, we should model organisms as a black box without internal experience. This idea, due to Skinner, is pretty idiotic.

In my view, positivism is an engrained part of science, and in my view, it has never steered us wrong, even in cases like S-matrix-theory/string-theory when almost everybody thought it did. With the presence of computers, and computer languages, formal languages are no longer abstract and remote. People program computers all the time. Scientists know when what they say has meaning when they can program a computer to do their model. So I think it is fair to say logical positivism is the only correct functioning philosophy.

All the logical positivists are now dead, and their work is basically ignored within their own field. If you ask philosophers why they ignore logical positivism, they often say: "Positivism contradicts itself. It says all truths need to be experimentally verifiable, but positivism is not experimentally verifiable!" To call this stupid, self-serving and intellectually vapid is too kind.

answered Aug 30, 2011 by (7,720 points)
edited Apr 12, 2014
"If the effects of acceleration are indistinguishable from gravity, then gravity and acceleration must be the same thing in essence..." By no means. If that is true then, because it is a very predictive statement, it should also be true this sentence: "If the effects of acceleration are indistinguishable from "motion in an electrostatic field"", then "electrostatic field" and acceleration must be the same thing in essence. They are distinct notions.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Helder Velez
@HelderVelez: The effects of accelerations for electrostatic fields are not indistinguishable unless all particles have the same charge as mass. Otherwise, you use a neutral particle to see that other particles are accelerating. But there is such a limit, in Kaluza Klein theory, in cases where all particles have the same momentum in the fifth direction, and it is precisely in this case that gravity and electromagnetism are welded together to make electrostatics a geometric force.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
@zyx: Then why would Skinnerian linguists treat language as a regular automaton? This is suggesting that they view the inner experience as a simple computation between input and output.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
@zyx: I agree with you in practical applications, and I also agree with the positivism, but the extreme idea that the internal computation must be extremely limited and modelled by the simplest automata that can reproduce the input output behavior approximately, I find uncompelling. I think the reason Comskianism fails is because there is false baggage with this idea (the statement that stack grammar is ancient) and also that the languages people use to parse languages are primitive. When Perl 6 comes out (the end of days!) maybe this will improve.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon

Yes, I own the original copyright. But perhaps ask on meta? Maybe others will want to know this, and make their own posts native, so there is less importing.

@Ron Maimon Hm, SE always says that SE owns the copyright for all the posts, but the posts are just "attributed" to the posters.

@ron This answer was commented and voted on in the other forum, so just copy and paste to make it native, to clean everything else. Thinking about it, I'm not sure if even that is ethically correct, since you're just copying and pasting.

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It's not really a single principle - it's a philosophy and in the context of philosophical discussions about science, it is usually known as positivism.

http://en.wikipedia.org/wiki/Positivism

As any philosophy, it cripples the penetrating power of science if it is extended too far - and every philosophy ultimately fails. The thought experiment about the Earth in the Universe is just one among millions of examples. Positivism could have a problem with the whole concept of thought experiments.

While it was very useful and important for the development of quantum mechanics to realize that science doesn't have to talk about things that can't be measured, i.e. that theories that deny the existence of things that can't be observed are just fine, it still remains true that science also can talk about concepts that can't be observed, such as quarks.

It's up to the scientific method to decide whether an auxiliary concept or a theory that isn't accessible to observations has an explanatory power that justifies its validity - and the answer may be different in each individual situation.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Luboš Motl
answered Jan 24, 2011 by (10,278 points)
Actually, physics is "natural philosophy"... :-)

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Sklivvz
@Noldorin: well, the claim that 'every philosophy ultimately fails' is itself a philosophical statement, anyway. (so I guess it's undeterminable)

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Jerry Schirmer
@Sklivvz: Hah, exactly! There were only "natural philosophers" up until the 19th century or so.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Noldorin
Quarks can be observed as well as anything else. Positivism does not forbid inference.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
The key word for positivism is «meaning». Positivism does forbid inferences to thing which cannot be measured, since it forbids us to even talk about them. It says all discussion of them, including inferences using them, are meaningless. Positivism was not actually very helpful in the development of QM: it inspired Heisenberg, but if he had never done it, Schroedinger would have, and Schroedinger was inspired quite differently.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user joseph f. johnson
That's right, Sklivvz. Physics is a natural philosophy while the other philosophy is either unnatural philosophy or man-made philosophy. ;-) Jerry: yes, the statement that "every philosophy ultimately fails" cannot be proved within the system, as dictated by Gödel's theorems. However, the proof that it's unprovable within the system also shows that it's true.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Luboš Motl
@Luboš: Physics is a natural philosophy but that doesn't prevent it from being man-made as well. Otherwise you identify physics with nature and don't view it as a process to study it.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user NiftyKitty95
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This is a very good question and we have very good discussions.

I feel that a meaningful scientific question should satisfies the following condition: The different answers to the question should have different measurable consequences.

Also a meaningful scientific statement should satisfies the following condition: The statement being true or false should have different measurable consequences.

For example, "a sign shows 'stop'" is a meaningful scientific statement since it can be tested by looking at the sign. But "What does a sign show before anyone looks at it?" may not be a meaningful scientific question. (Or is it?) This kind of issue appear in the measurement theory of quantum mechanics.

How to ask a meaningful scientific question? One may first think about what the potential answer might be. Then try to design an experiment to test the validity of the answer. A scientific question is meaningful or meaningless depend on the ability to design an experiment that can test the validity of its potential answer.

Here is an example: "Is existence timeless or in time?" The potential answers are: Existence is timeless and Existence is in time. The next task is to design an experiment to test the validity of the statement "Existence is timeless" or "Existence is in time". Here I have trouble. I do not know what experiment can test the validity of the above statement. Being able to design such an experiment will make a great scientific progress. One big area of scientific research is to design such kind of experiments and to make those used-to-be meaningless questions meaningful.

Not having such an experiment, the question is not a meaningful scientific question. The burden is on the person who ask the question to provide the experiment that, at least in principle, can test the validity of the potential answer.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Xiao-Gang Wen
answered May 28, 2012 by (3,485 points)

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user NiftyKitty95

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Xiao-Gang Wen
By "have measurable consequences", I mean "can be tested by experiments". "the sign is red" and "the sign is blue" do have measurable consequences. They can be tested experimentally by looking at the sign.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Xiao-Gang Wen
Okay, I see what you're saying. Although your use of the term "consequences" is a little unconventional. By this undestanding, the mere statements "This desk is a red.", "This desk is blue." and "this desk is not red." all have consequences. Baiscally, I can map colors to the reals and say arbitrary many sentences, which all have "consequences".

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user NiftyKitty95
@NickKidman: this is not always the case as in the example of certain widely accepted postulates for instance the rest mass of a photon as observing a photon at rest is not possible or measurable but somehow it is still generally accepted

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Argus
@Argus: What is not always the case? What is the context for the exmaple? If you want to explain it to me, please open a chat discussion. (Besides, I don't understand the sentence - you should break it in two or use commas. You don't even say what it is, which is generally accepted.)

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user NiftyKitty95
@NickKidman: Asking questions about non testable things is not always the case. Your Title . The fact that light has mass at rest is asked and used in many equations but the ability to test or measure that mass is not possible.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Argus
@NickKidman: openening chat

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Argus

## SE-user Argus :    We do have experimental methods that determine the quantity "rest mass". The exact terminology isn't important, it's just a name. As long as there is an experimental method of measurement we can call it anything we want.

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I'm not an expert on philosophical terminology, but I'd go for operationalism.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ted Bunn
answered Jan 24, 2011 by (140 points)
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Old answer: the "verification principle". The context was positivism, operationalism, or instrumentalism. The idea was that if a statement cannot be empirically verified it cannot be said to have meaning. This "principle" fell by the wayside when philosophers such as Bertrand Russell realized that the principle itself could not be empirically verified.

Recent: Please see the excellent discussion of this question in the context of string theory by Gordon Kane in the Nov. 2010 issue of Physics Today.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user user1580
answered Jan 25, 2011 by anonymous
The argument "verificationalism cannot be verified" is ridiculous. Verificationalism does not need to be verified, it is a definition of what it means to have knowledge. Everything other than this needs to be verified. It's like saying "you proved this from Euclid's axioms, but how do you prove Euclid's axioms?" You don't prove an axiom, you accept an axiom. Russell was not hostile to verificationalism anyway. You are probably thinking of the elder Wittgenstein, who broke with the positivists (some would say, and "some" includes me, that he sold out positivism).

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
+1 because this is the only answer that is correct - the term is "verification principle". "Positivism" means something much more specific. Positivism had the verification principle at its core, but also included all sorts of other stuff about null hypotheses and the propensity interpretation of probability theory, all of which sounded good at the time but has now been pretty much superseded by Bayesianism in most practical applications. However, I agree with Ron that "the verification principle cannot be verified" isn't a good argument, since the principle isn't a statement about the world.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Nathaniel
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Positivism, in this context, hinges on the principle that

« the meaning of a statement is the way you would verify it. »

(Or falsify it... the variations between verificationism and falsificationism are too small to warrant attention in this answer, which is trying to focus on the big picture.)

So the definition of a concept has to be laying out how you would measure it or experimentally verify it. It inspired Einstein (through Mach) and Heisenberg, but not Dirac or Schroedinger. Einstein later abandoned it, saying « one must not repeat a good joke too often ». Nowadays, most scientists would say that laying out how you would verify a concept is its operationalisation, not its meaning or definition.

To understand this principle, contrast it with Wittgenstein, who was never a positivist. Wittgenstein, as a good engineer and student of Hertz, said that

« the meaning of a proposition is the state of affairs which would hold good if the proposition were true.»

According to Weinberg in Dreams of a Final Theory, most physicists have by now abandoned positivism. According to Feynman in his Physics Lectures, positivism is false: he gives the same reasons as prof. Motl but states them even more strongly.

But where Dirac and Heisenberg agree, and some posters here, too, is that what we have learned is that if an objection to a scientific theory cannot possibly be re-cast into experimentally verifiable (and replicable) form, then the scientific theory should not be rejected simply because of that objection.

(Wienberg, Dreams of a Final Theory, p. 181: «The positivist concentration on observables like particle positions and momenta has stood in the way of a "realist" interpretation of quantum mechanics, in which the wave function is the representation of physical reality.» See also pp. 167, 304. Feynman, Lectures on Physics vol. III, p. 2-8: «the idea that we should not speak about those things which we cannot measure. ... The idea that this is what was the matter with classical theory is a false position

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user joseph f. johnson
answered Dec 17, 2011 by (500 points)
I agree with you on the numbers, but the real reason Feynman abandons positivism is because it led to Chew, Frautshci, Mandelstam physics, and he hated that stuff. The thing is, that stuff is now called string theory, and without positivism, you can't make sense of string theory. So while you are right that physicists don't say they are positivists, they are deep down inside anyway. All physicists are, and will always be verificationalist positivists period.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
Also, Dirac was certainly fine with positivism, it went without saying in those days. Positivism was the normal standard philosophy until about 1975 or so. It is depressing that we've actually gone backwards a little--- philosophers sitting around a haze of marijuana smoke, saying "Dig, How can I know that the feeling of seeing red that you see is the same seeing red feeling that I see, like, in positivism, man?" What a waste.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
I said Dirac was not inspired by positivism.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user joseph f. johnson
I am not sure about this. Dirac followed heisenberg in the observable/matrix quantum mechanics, which was directly inspired by positivism. I agree it wasn't the major driving force behind his research, but he doesn't postulate unmeasurable quantities, as others who reject positivism have done. In particular, Feynman's rejection of positivism is based on the feeling that off-shell operators are meaningful, a feeling shared by Mandelstam and others, which is true in field theory, but false in string theory.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
I am. (first note inspiration is not transitive). He was inspired by the beauty of Heisenberg's equations and the parallel with Poisson Brackets. did he not postulate unmeasurable constructs? he, famously, thought that the state vectors were real, that the Hilbert space of the Universe was genuinely, um, actual (complex), that a piece of chalk was always in a pure quantum state and could even be in a superposition of states, one localised here, and the other localised there. which is precisely what led him to postulate the collapse of the wave function as a real physical process. (I disagree.)

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user joseph f. johnson
That's interesting--- I didn't know Dirac's position on the reality of the wavefunction. I read a lot of Dirac too, and he seemed to keep mum, from what I read. Could you paraphrase something he said with regard to this? The statement that the universe has a wavefunction and can be in a superposition is usually attributed to Everett, and it doesn't come with a collapse as a physical process, but with a many-worlds subjective psychological collapse, which only appears to happen for large thermodynamic observers.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
More precisely: google on chalk and you'll find that one. The universe one is well-known Cambridge lore, but I can't remember where I read it. The 'reality' of the state vector is not there in so many words, but in light of this discussion you should re-read his 'deduction' of the collapse postulate from physical principles, epecially where he invokes what he literally calls «the principle of physical continuity» or something like that to prove the wave function has to collapse. !!! NOne of this is to deny that he was 'comfortable with positivism', just not a committed consistent positivist.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user joseph f. johnson
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In academic philosophy this is called metaphysical antirealism: the position that

that which is in principle unknowable, is meaningless.

Examples that are sometimes given:

• "My qualia when I perceive the color "blue", say, are different from yours"
• "When Julius Caesar was born, he was first put down to lie on his tummy and not on his back".
answered Apr 27, 2017 by (10 points)
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There is a difference between to measure and to test.

If something can't be measured (by devices or the senses) it is not a scientific concept according to old positivism. Pure positivism in use was/is for instance operationalism which thus meant that a concept is meaningful only if we have some way to measure it.

The way a theory can or cannot be tested has more to do with the scientific method. According to Popper a theory is not scientific if it can't be falsified in contrast to positivists considering a theory scientific if it (among other things) can be proved true by confirmation.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user curious
answered Jan 25, 2011 by (505 points)
+ 1 like - 1 dislike

"It is pointless/meaningless to try to talk/question things that can not be tested/measured" is not a principle!

It suffers from itself. It's founded upon circular argument. In most uses (e.g., the historically claimed sentiment that atoms don't exist), it's founded on an inductive fallacy as well; that which is not measurable on one's particular instrument is mistaken for being not measurable on any instrument.

Anyway, there's something to learn from philosophers and statisticians who have spent some time on this.

answered Feb 11, 2016 by (0 points)

This is a standard, nonsensical criticism of positivism that has been answered multiple times in this thread. The claim that it says "atoms don't exist" is also wrong, because you can observe the effects of atoms, even if you were unable to directly observe them. Positivism doesn't choose metaphysical formulations, it says that all metaphysical formulations are equivalent and that asking "do quarks really exist or does matter just behave like they do?" is nonsense.

@dimension10: My comment was about the statement I quoted not positivism or metaphysics. My point is simply there is no way to determine a priori whether something is untestable. The most one can say is that they don't know how to test it.

"The statement [you] quoted" is (logical) positivism. The "test of untestability" is not empirical, it comes under the "logical" part of logical positivism.

For instance, "a bearded old man runs our universe as a simulation on his computer" is not testable because it isn't formulated coherently with precise instructions for testability, but "if you tap your foot five times, you will see yourself coming out of a computer and a beard man in front of you" is testable.

Logical positivism just says that all metaphysical formulations are equivalent as long as they give you the same predictions. Telling a physicist you can't test if something is testable is equivalent to telling a programmer that you cannot know if a bug can be reproduced.

Saying "logical positivism is not testable" is an abuse of language, in the same way that saying "the idea of gauge invariance is not gauge invariant" is an abuse of language.

So your test of untestability is whether or not a hypothesis includes instructions for how to test it. Another thing to note is that an ill-defined or incoherent statement is not a hypothesis.

@jima Exactly, that's the "logical" part of logical positivism -- "logical" here means mathematically precise.

You can call it a "test for untestability" or whatever you like, but it's exactly what physicists have been doing since about the mid-1500s. Atoms, for instance, are considered testable because the results could be seen in Browinian motion. You can formulate it in any way you like, saying that it's not really atoms but just pretending to be atoms or whatever the philosophers' fluff says, but in logical positivism all these metaphysical formulations are equivalent.

+ 0 like - 3 dislike

A positivist will tell you only questions which can be answered in terms of my empirical sense perceptions right now can have meaning. Other questions are meaningless.

For example, is there an objective world out there going more or less as my sense perceptions seem to tell me they are, or is reality really completely different and I am on an acid trip hallucinating my current sense perceptions, or am I a computer program having a cyberdelic electric dream in a virtual reality temporarily taking on the persona of a human? Positivism will command you to reject this as a meaningless question. A mere bunch of words evoking some thought patterns in the brain! Aah, I might not be able to tell now, but in the future, when I wake up, I will be able to tell? Nonsense! Meaningless gibberish, says the positivist. There is no empirical experience of the future right now. Another meaningless question. The future is meaningless. I might as well go read a Phillip K. Dick story... except maybe I am a character in a Phillip K. Dick story I have not read (because that would spoil the script), and some advanced technology in the 22nd century allows people to have immersive first hand experiences of fictitious characters brought to life... Can I perform a test to measure the difference? No! Another meaningless question to be tossed into the trash can.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Very Suspicious Character
answered May 31, 2012 by (-30 points)
You are making a caricature of positivism, but it is an axiom of thought. It does not require you to say that reality is real, it does not require you to say that you are hallucinating it, it allows you to say either, and to believe both, and to translate between the two positions and see that there is no real difference between them. This is like a gauge transformation for philosophy, and the true philosophy has to be gauge invariant. The philosophy people debate is "I want realist gauge", "I want instrumentalist gauge", and this gets tired quickly.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Ron Maimon
"There is no empirical experience of the future right now." ??? ALL the PAST is an "empirical experience of the future" because any past moment is in the future of an infinite previous moments. By no means I can say that this moment of now, and the ones in the future are different from the ones in the past. There is no basis to argue that 'talk/project' the future is meaningless.

This post imported from StackExchange Physics at 2014-04-04 16:53 (UCT), posted by SE-user Helder Velez

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