There are many questions in philosophy of the following kind:

  • Does my friend have a soul, or is my friend a zombie?
  • Is the mind separate from the body, or is it the same?
  • Where does the universe come from?

These questions have the property that, whatever the hypothetical answer would be, every one of your perceptions of the world is exactly the same.

It is a central tenet of Carnap and the positivists that one should consider such questions as meaningless, as an abuse of language. This position answers or moots most of the questions on this site. Positivism was accepted for a while in philosophy, but no longer. I am shocked by this.

Is it still considered correct that a question with no perceptible difference one way or another (like, "Are you a zombie?") is inherently meaningless? Why would anyone assign meaning to such a question?


These questions have the property that, whatever the hypothetical answer would be, every one of your perceptions of the world is exactly the same.

That is absolutely untrue. My perception of the world might be profoundly different if I knew with certainty information regarding the existence of souls, or the independence of mind from body, or the source of the universe.

These are not trivial matters.

One could just as easily say that it makes no difference whether string theory is correct or not, as it makes no perceptible difference to one's life.

Is it still considered correct that a question with no perceptible difference one way or another [...] is inherently meaningless?

Could you provide a legitimate example of a question with no perceptible difference one way or another?

Positivism was accepted for a while in philosophy, but no longer. I am shocked by this.

Why does this shock you? There have been many critiques of positivism, and virtually everybody (including many former positivists) believe that philosophy has moved forward since positivism's heyday. A.J. Ayer, in fact, famously said "I suppose the most important [defect]...was that nearly all of it was false."

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    String theory has a perceptible difference--- it predicts things about black holes, probably that rotating ones emit stuff that is nonthermal. It also predicts the results of high energy experiment. I am saying that even if someone were to assure you that everyone except you does not have a soul, it wouldn't make one whit of difference, since the statement "X doesn't have a soul but behaves indistinguishably" is meaningless in the sense of Carnap. I agree positivism is counterintuitive and smashes through BS: this is why it was so revolutionary. It is also why it is such an unpersuasive truth. – Ron Maimon Apr 18 '12 at 20:42
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    The differences in "preception" that you are talking about are not differences in obsevations or response to these, but a different set of words knocking around your cerebrum about what concept words to attach to these perceptions. Attaching different concept words to the perceptions in thier amalgamations does not constitute a change in anything by psychology, and reason shouldn't depend on your chosen category system or method of naming preceptions or thier correlations. – Ron Maimon Apr 19 '12 at 0:12
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    "X doesn't have a soul but behaves indistinguishably" is meaningless in the sense of Carnap, but highly meaningful to, say, Augustine or Aquinas. Furthermore, the view that "reason shouldn't depend on your chosen category system or method of naming perceptions" is an incredibly naive view. – Michael Dorfman Apr 19 '12 at 6:38
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    You say "naive", I say "incredibly sophisticated". Look at how Augustine and Aquinas stupidly missed it. Positivism is a 19th century idea, probably due to Mach, and that it is reasonable is basically equivalent to persuading a solipsist (who believes the world ends after death) to buy life insurance. I believe that the superrational argument for life insurance would work equally well for a solipsist, a Christian, an atheist, an agnostic, or any other metaphysical stance you can imagine, since it is postivist, and can be translated from one metaphysics to another with ease. – Ron Maimon Apr 19 '12 at 7:01

These questions have the property that, whatever the hypothetical answer would be, every one of your perceptions of the world is exactly the same.

(emphasis mine).

You have imported an assumption here that, I think, explains why all of your examples are problematic.

What precisely do you mean by the world? If souls are real, and they (we) exist after death, does the world include the post-death environment of the soul, or not? If no, why do you privilege existence-as-soul-plus-corporeal-physical-form above existence-as-soul-in-post-death-environment? If yes, is it necessarily true that you have to find evidence pre-death, or can you wait until post-death to make the call?

So I think these are sensible questions to ask, even if, after a long detour that requires one to rethink one's epistemology, one concludes that the answers are, "no zombies or the question is meaningless; the mind is the same as the body or the question is meaningless; the origin of the universe is an insensible question unless you're redefining universe". You don't just (or many people do not) end up there intuitively, so the questions are reasonable to ask even if at the end you conclude, "Well, that was all just confused, wasn't it?"

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    If you want my definition of "the world"--- it's what I can see, or talk to people, or forseeably figure out in principle, but figure out and transmit to others through writing or art or some other information transmission scheme. You can't use life after death in planning, because you have no reliable evidence for what its like. So even if you believe in it, you can't predict what behavior will benefit you in the post-life if that post-life is unobservable. The post-life which you can see is the post-life of people is in their information footprint on others. This is observed, and relevant. – Ron Maimon Apr 19 '12 at 5:33
  • @RonMaimon - That is a pragmatic view but I don't think it's a trivially obvious view since arguments about whether one should plan for the future start out very much the same way as planning for what happens to your soul, and it takes quite a bit of thought and reasoning until you hit the place where they diverge. – Rex Kerr Apr 19 '12 at 14:12

It can be very meaningful, and just how meaningful will vary depending on the person and the question. Even if it doesn't alter the observable (physical) world ("your perceptions of the world"), it is still meaningful if it alters human behavior. In fact, it is strange to me that you don't seem to consider human behavior as a "perceptible difference" of the world.


Does God exist?

  • If God does exist, then the way things are in the world is exactly as he planned. He is here and has always been here.
  • If God does not exist, then the world keeps on ticking, exactly as it has this whole time.

However, while the world/universe doesn't change, our behavior towards the world can change. For example, if I was provided solid evidence for the existence of God, I would radically change my life in order to conform to his will (if we are talking about the Christian God, perhaps I would start praying, repent for my sins, attend Church more, etc.).

  • "…if I was provided solid evidence for the existence of God…" But what solid evidence could this be other than some kind of perceptual belief (if we follow the OP's constraints)? And if this evidence was based on some kind of observation, then the question "Does God exist?" would be indeed "a question with perceptible difference". A world in which God physically exists would be rather different than one in which (s)he does not. Did I miss something? – DBK Apr 18 '12 at 20:27
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    There are people who believe that God exists, and those who believe that there are no Gods. The "world" that both these people share is perceptually the same, and yet their beliefs radically differ. The fact that people switch sides all the time, gaining and losing faith, is testament to the fact that there is enough compelling evidence one way or another (for that particular person), and yet the world is still perceptually equivalent to both groups. My point here is thus that beliefs—and therefore behavior—can still change, even if the world remains "observationally equivalent". – stoicfury Apr 18 '12 at 20:45
  • @DBK: I believe that the metaphysical aspects of God, whether the gates are pearly, or whether there is water in heaven, are indeed meaningless in the sense of Carnap, but the ethical aspects of God are not. People conflate the two. I said how God works in the logical positivist perspective here. It has manifestations in the observable (these manifestations are all I use)--- it is the ethics of the future, and the ethics of covergent limiting superrationality. – Ron Maimon Apr 18 '12 at 20:45
  • @stoicfury: I believe that the people who change with regards to belief in God, so long as that is a purely metaphysical belief, cannot come to any rational conclusion that is different from the atheist. If they believe that God will smite the wicked, they might change, but then the smiting is observational. Regarding afterlife, if they think God makes a heaven, maybe only the atheists get to go to heaven (God is mysterious). Only if they believe in something non-metaphysical can it make a difference. The only non-metaphysical thing I see is the notion of a convergent superrational ethics. – Ron Maimon Apr 18 '12 at 20:46
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    "But if that belief is not observationally grounded, no sound reasoning can come to good conclusions, because any one conclusion is as good as any other in the absence of evidence." But there are a lot of people who would disagree with this. Many think you can derive very firm conclusions purely from ratiocination; and the extent will vary from person to person based on their own epistemology. Don't get me wrong, I for the most part agree with you here, but I think the distinctions you raise still have meaning because they have the power of altering behavior. – stoicfury Apr 18 '12 at 23:52

Logical Positivism, seems to me a philosophy that evolved by taking the scientific viewpoint as the only legitimate way to ask meaningful questions. Its greatest failing is that its not very imaginative. Its an interesting perspective to hold for a while, but to hold it exclusively feels severely limiting.

Also, historically its not even true as to how science developed.

Leucippus came up with the atomic theory without any hope of establishing the truth of his hypothesis until 2 millenia later.

The hypothesis of a spherical Earth, established in antiquity, but not observationally verified until the first circumnavigation of the earth.

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    Well, positivism is a method of ensuring you know what you're talking about in science. If you are talking about the electron with a position and a velocity, you need to know you can determine the position and velocity, and if you find you can't, not even in principle, you reject the idea that the electron has both simultaneously. As far as atomism, I find the ancient arguments for the sphericity of the Earth (always round shadow on the moon, high towers see farther as the square root of the height times the Earth's radius, lattitude differences in sun's position) completely positivistically – Ron Maimon Apr 19 '12 at 3:02
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    compelling. The arguments for atomism (breakdown and reconstitution of biological material according to definite invisible patters, sharp phase transitions between different phases, random motion of small particles) are less compelling, as they don't estimate size. These positions (and the ancient heliocentrism of Aristarchus and Appolonius) were rejected solely based on politics and theology, not based on compelling reasoned arguments. The scientific revolution of the enlightenment was only rediscovering and rearguing for a hundred years or so, but in a better politics. – Ron Maimon Apr 19 '12 at 3:05
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    The feeling of limitation is largely illusiary. Positivism is very imaginative--- it imagined a computer before the first one was built, it imagined that there are real, actual Electric and Magnetic (and Gravitational) fields based on the fact that they can be measured (others did not admit the field was real), it is the source of the relativity principle, the uncertainty principle, and the S-matrix/holographic principle in physics, and the computational theory of mind in philosophy. – Ron Maimon Apr 19 '12 at 3:13
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    @MozibarUllah: These arguments were listed by Aristotle--- the ship's mast is seen from land first (the guy on the mast can see land before the guy on the deck--- the distance goes as the square root of the mast-height), the shadow of the Earth is also given by ancient astronomers (it's on Wikipedia somewhere), the lattitude difference of the sun's position was used by Aristarchus to give the radius of the Earth to 10% accuracy. Positivism is not hard to stomach--- it's obvious--- and it used to be well accepted. I am not sure hidden variables are wrong (Bell only disproves local HV's). – Ron Maimon Apr 20 '12 at 0:35
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    The evidence from string theory comes from the known quantum mechanics and known General Relativity--- there is no other plausible way to make a quantum theory of gravity. It has passed an impossibly stringent test--- it reproduces GR in the classical limit, with consistent black holes, and includes QM. I believe we will gain evidence in time for string theory (or against), and the major hurdle is that our techology cannot directly probe the energies. As for spherical Earth--- how can I speculate about reasons that don't appear in print? What other reasons are there? – Ron Maimon Apr 20 '12 at 6:32

I think that methaphysical theories (non testable in principle) are necessary and important to scientific research because they may be capable of becoming physical (testable in principle) theories.

Of course, if you understand clearly that your answers are completely equivalent experimentally, then you are saying just the same in different ways, you get into a purely formal ground, like when we state the equivalence of two different formulations of the same physical theory; but it may happen that the possible ways of showing the difference empirically are still not understood - think about the Aharonov–Bohm effect, e.g.


"no perceptible difference one way or another"

To the senses, "no perceptible difference". To the intellect? Profound perceptible differences!

Nothing to be shocked about.

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    Anything which has perceptible differences to the intellect need to have perceptible differences to the senses. This is the common sense axiom of logical positivism, and it is important to not willfully forget it, even if philosophical winds have changed and people feel like ignoring this insight. – Ron Maimon May 14 '13 at 1:42
  • "and it is important to not willfully forget it" . I don't forget it. I categorically deny it - it is nonsense IMO. – Vector May 14 '13 at 1:45

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