If you treat your postulates like hypotheses, you wind up talking nonsense

Physics postulates a world explicable under the category of measurable quantities. Any such quantities it finds will be deemed "physical." The fact that everything physics finds is explicable in terms of the physical is not a hypothesis that physicists are testing, it is an assumption of their science.

As such it is ridiculous to point to the work of physicists as "evidence" for a philosophy which one may refer to as "naturalism." It is not a flaw of physics or physicists to make this assumption. What forms any particular science is the set of postulates which it makes about the world, and through which it proceeds to investigate the world as it is seen under those postulates. But it is a mistake to forget that these are postulates and not discoveries.

Consider an episode like the discovery of the weak nuclear force. Certain measurable phenomena cannot be explained through any of the other known forces. These phenomena have weird characteristics: certain parities that are usually maintained are violated, and quarks change their flavor. So physicists postulated the existence of a force that would produce these phenomena.

Now perhaps what was "really" going on was the God, having nearly finished creation, thought to himself, "I can foresee these people called physicists, who are going to think their theories explain everything. So let me continually cause the universe to behave in such a way that certain parities are regularly violated, and quarks change their flavor. That should shake them up."

So long as God did this in a measurably regular way, what we would see would be no different than if these things are caused by a "weak nuclear force." But physicists proceed by postulating things like heavy bosons and a weak nuclear force. One may protest, "But physicists are able to draw new predictions from their idea of these phenomena arising from a force!" That is great, and it is why physicists should continue to postulate forces. But the end result is not distinguishable from a case in which God was "fiddling" around with things in a regular, predictable way that hinted at further regularities to be detected.

Or consider the partial confirmation of Bell's theorem by Aspect et al. One might view this result and conclude, "Well, God just keeps these spatially separated particles correlated." But what many physicists have decided is that "local realism" is false. Now, local realism was a linchpin of the very idea of a "physical world," which is why Einstein and his colleagues proposed their original thought experiment, intending it as a way of showing that quantum mechanics must be incorrect in some way. But in the face of Bell and Aspect, what most physicists have done is simply to alter their idea of what "physical" reality is like.

Once again, I am not criticizing physicists for proceeding in this fashion: this way of proceeding is the very thing that creates physics as a distinct world of ideas. What I am pointing out is that is no more significant that physicists find everything in the world of physics explicable by physical principles than it is that Swahili speakers find everything in their world adequately described in the Swahili language. Swahili is, I am sure, a fine language, and I bet it describes the world quite well. But it would be a terrible error to leap from that fact to the conclusion that the world is actually built out of Swahili words and phrases.


15 comments:

  1. Hence Occam's Razor. Postulate the regularity, the force, and stop there.

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    1. Well, except "the force" is a postulate well beyond the regularity, as Hume so clearly noted!

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    2. Yes, I meant assume that the regularity you see is there because of an underlying regularity, which we call the force. The usual inductive assumption.

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  2. Gene isn't it a significant and nontrivial fact that a large and ever-growing number of aspects of our sensory experience can be predicted using mathematical quantities? We can predict what color something will look, whether it will look big or small, whether it will move fast or slow, whether it will feel rough or smooth, what a dial on a measuring device is going to show, etc. Couldn't we have easily been born in a universe in which that wasn't the case?

    In an old post I didn't get a chance to respond to, you asked me whether I could rule out the possibility that humans are describable entirely by age and gender, since advertisers can predict so much about a person's shopping habits from those two numbers. I think the difference is that that only predicts a tiny sliver of our experience, whereas the quantities of natural science can predict so much of what we observe. So that lends plausibility to naturalism, even if alternate explanations of the regularity are possible.

    I should reiterate that I'm not actually a naturalist. I'm just playing devil's advocate.

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  3. Keshav, I have never said physics is useless! Before from making naturalism plausible, naturalism makes the fact this occurs incomprehensible.

    In any case, the predictions of physics actually have a limited validity in the real world... see Nancy Cartwright, How the Laws of Physics Lie. In terms of predicting the actual behavior of people, I'd say marketers have the physicists crushed. So if this makes naturalism plausible, it makes "maketerism" much, much more plausible!

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    1. "Keshav, I have never said physics is useless! Before from making naturalism plausible, naturalism makes the fact this occurs incomprehensible." Why is that? Surely if you're a naturalist you would expect that physics makes accurate predictions.

      "In any case, the predictions of physics actually have a limited validity in the real world... see Nancy Cartwright, How the Laws of Physics Lie." I haven't read Cartwright's book myself, but based on what I've heard from people who have read it, her argument is that e.g. the theory of gravity doesn't tell us anything about reality because it just says that all other things being equal the force on an object is this much greater than it otherwise would be in the absence of gravity. But I don't see how that's so devastating, when we can still make approximate predictions.

      "In terms of predicting the actual behavior of people, I'd say marketers have the physicists crushed. So if this makes naturalism plausible, it makes "maketerism" much, much more plausible!" But the shopping habits of humans is such a tiny sliver of our sensory experience, compared to the myriad things that the physical sciences make predictions about. So it's much more plausible that the physical sciences will one day make accurate predictions about all aspects of our sensory experience, if they're already capable of explaining so many aspects and the list keeps growing.

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    2. Ok, Keshav, I am going to do a top-level post about the incomprehensibility issue.

      But let me say I find your harping on prediction itself incomprehensible. Let us say I develop a system that predicts football games extremely, extremely well: I go through an entire NFL season, and basically don't get a game wrong. Based on this result, I declare, "Games of football don't really exist: the only thing that really exists is my game predicting system!"

      Isn't it obvious that this is logical nonsense? If sensory experiences don't "really" exist, then what the hell are the laws of physics accurately predicting?!

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    3. "If sensory experiences don't "really" exist, then what the hell are the laws of physics accurately predicting?!" Gene, what if the external world consists of things describable entirely by numbers, and then those numbers are translated by some sort of lookup table into sensory experiences for the mind? In that case, assuming that physics allowed you to predict what those numbers are going to be, you could completely predict what a person experiences.

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    4. Keshav, if the real world consists entirely of numbers, can you please explain to me how the numbers can have sensory experiences? Your suggestion makes as much sense to me as someone saying "what if cars were really cows and milk was really the square root of two?"

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    5. I was going to post something, Gene - and I'll await your coming post on conceivability - but wow. I have to say that some of the comments are here are just plain bad philosophy (read: there is some pretty bad thinking going on here.)

      Keshav, have you read *any* philosophy, especially philosophy of science...?

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  4. Well, what if dualism was true, and everything outside than the mind is describable by numbers, and the numbers are translated into sensory experiences in the mind?

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    1. Ok Keshav, but dualism is precisely what (most) naturalism seeks to deny.

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    2. By the way, Keshav, what you describe is very much the position of the Cartesians, we were NOT adherents of naturalism.

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    3. Yeah, fair enough. Dualism and complete naturalism contradict each other. But what is your objection to the argument that the success of the physical sciences in predicting more and more aspects of our sensory experience lends plausibility to naturalism at least holding for phenomena other than the mind?

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    4. I don't think "naturalism holding for phenomena other than the mind" has any coherent meaning: once you are a dualist, you have abandoned naturalism! It is like saying, "I am a law-abiding citizen accept on all those occasions where I commit crimes."

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