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Bugmaster comments on How to Not Lose an Argument - Less Wrong
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Ah, yes, agreed.
I think I might be misunderstanding what the word "incommensurability" means. I thought that it meant, "the performance of theory A cannot be compared with the performance of theory B", but in case of Aristotle/Newton/Einstein, we can definitely rank the performance (in the order I listed, in fact). Aristotle's Laws of Motion are more or less (ok, closer to the "less" side perhaps, but still) useful, as long as you're dealing with solid objects on Earth. Their predictive power isn't great, but it's not zero. Newton's Laws are much more powerful, and relativity is so powerful that it's overkill in many cases (f.ex. if you're trying to accurately lob a rock with a trebuchet). Each set of laws was devised to explain the best evidence that was available at the time; I see nothing incommesurate about that. But, again, it's possible that I'm using the word incorrectly.
I am not convinced that they are. In fact -- again, assuming I'm using the word correctly -- how can theories be incommesurable and yet falsifiable ? And if a theory is not falsifiable, it's not very useful, IMO (nor is it a theory, technically).
As I use incommensurability, I mean that the basic concepts in one theory cannot be made to correspond with the basic concepts of another theory.
At bottom, Aristotelian physics says that what needs to be explained is motion. In contrast, Newtonian physics says that what needs to be explained is acceleration. I assert that there is no way to import principles for explaining motion into a theory that exists to explain acceleration. In other words, Aristotelian physics is not a simpler and more naive form of Newtonian physics. You can produce a post-hoc explanation of the differences like your invocation of the limits of observable evidence (but see this discussion). I find post-hoc explanation unsatisfying because scientists talk as if they can ex ante predict (1) what sorts of new evidence science needs to improve and (2) what the "revolutionary" new theories will look like. And yet that doesn't seem to be true historically.
There is some unfortunate equivocation in the the word theory ("Theory of Gravity" vs. "Utilitarianism: A Moral theory"). But something like Freudian thought is unified(-ish) and coherent(-ish). What is wrong with referencing "Freudian theory"? That doesn't reject Popper's assertion that Freudian thought isn't a scientific theory (because Freudian thought isn't falsifiable). On falsifiability more generally, I'm not sure what it means to ask whether utilitarianism (or any moral theory) is falsifiable.
What about "V = a * t" ? That said, AFAIK "at bottom" Newton didn't really want to explain acceleration, or motion, or any abstract concept like that; he wanted to know why the planets appear at certain places in the sky at certain times, and not others -- but he could pinpoint the position of a planet much better than Aristotle could.
And I think we can, in fact, correspond Newtonian concepts to Aristotelian ones, if only by pointing out which parts Aristotle missed -- which would allow us to map one theory to the other. For example, we (or Archimedes, even) could talk about density and displacement, and use it to explain the parts that Aristotle got right (most rocks sink in water) as well as the parts he got wrong (actually some porous rocks can float).
Nothing really, it's just that most people around here, AFAIK, mean something like "a scientific, falsifiable, well-tested theory" when they use the word.
If it's unfalsifiable, what good is it ? Isn't that the same as saying, "it has no explanatory power" and "it lacks any application to anything" ?
I see utilitarianism as more of a recipe (or an algorithm) than a theory, so it doesn't need to be falsifiable per se.
For theories to be commensurate, you need to be able to move all the interesting insights of each theory into the other and still have the same insight. Sure, Aristotle and Newton seemed to agree on the definition of velocity and acceleration. But there's no way to state "An object in motion will tend to stay in motion" as a conclusion of Aristotelian physics because the caveats Aristotle would want to insert would totally change the meaning.
(As an aside, I'm making a point about the theories, not the scientists. Boyi might find Newton's motivation interesting, but I'm trying to limit the focus to the theories themselves).
The point about moral "theory" is sufficiently distinct that I hope you'll forgive my desire to move it elsewhere just to make this conversation easier to follow.
In this case, I don't think I fully understand what you mean by "insights" being "the same". Any two scientific theories will make different models of reality, by definition; if they didn't, they'd be the same theory. So, if you go the extreme route, you could say that all theories are incommensurate by definition, but this interpretation would be trivial, since it'd be the same as saying, "different theories are different".
I agree that there's "no way to state 'An object in motion will tend to stay in motion' as a conclusion of Aristotelian physics", but that's because Aristotelian physics is less correct than Newtonian mechanics. But there is a way to partially map Newtonian mechanics to Aristotelian physics, by restricting our observations to a very specific set of circumstances (relatively heavy objects, an atmosphere, the surface of Greece, etc.). Similarly, we can map relativity to Newtonian mechanics (relatively heavy objects, slow speeds, etc.). It seems odd to say that these theories are totally incommensurate, while still being able to perform this kind of mapping.
In fact, we perform this kind of reduction every day, even in practical settings. When I want to drive from point A to point B, Google Maps tells me that the Earth is flat, and I implicitly believe that the Earth is flat. But if I want to fly to China, I have to discard this assumption and go with the round-Earth model. I see nothing philosophically troubling about that -- why use an expensive scalpel when a cheap mallet works just as well ?
I was trying to make a point that scientific theories are not just about moving abstract concepts around; their whole purpose is to make predictions about our observations. This is what differentiates them from pure philosophy, and this is also what makes it possible to compare one theory to another and rank them according to correctness and predictive power -- because we have an external standard by which to judge them.
Yeah, that's a good move, no objections here.
But not too heavy...
Haha, yes, very important detail, that :-)
I can't write it better than Feyerabend. My argument about Aristotelian and Newtonian physics is a paraphrase of section 5 of his argument, starting at pg. 94, and ending at about 101.
ETA: And I looked at it again and it's missing 95-96, where some of the definitions are. If there's interest, I'll type it up, because I think it addresses the criticisms fairly well.
Ok, I have to admit that I haven't read the entire book, but only skimmed the section your mentioned -- because my time is limited, but also because, in its infinite wisdom, Google decided to exclude some of the pages.
Still, I can see that Feyerabend is talking about the same things you're talking about; but I can't see why those things matter. Yes, Aristotle had a very different model of the physical world than Newton; and yes, you can't somehow "plug in" Aristotelian physics into Newtonian mechanics and expect it to work. I agree with Feyerabend there. But you could still go the other way: you can use Newtonian mechanics, as well as what we know of Aristotle's environment, to explain why Aristotle got the results he did, and thus derive a very limited subset of the world in which Aristotle's physics sort of works. This does not entail rewriting the entirety of Newtonian mechanics in terms of Aristotelian physics or vice versa, because Aristotle was flat out wrong about some things (a lot of things, actually). Feyerabend seems to believe that this makes the two theories incommensurate, but, as I said above, by that standard the word "incommensurate" becomes synonymous with "different", which is not informative. I think that Feyerabend's standards are simply too high.
I was also rather puzzled by something that Feyerabend says on page 98, toward the bottom. He says that "impoetus" and "momentum" would give you the same value mathematically, and yet we can't treat them as equivalent, because they rest on different assumptions. They give you the same answer, though ! Isn't this what science is all about, answers ?
Let me illustrate my point in a more flowery way. Let's say that Aristotle, Newton, and Einstein all went to a country fair together, and entered the same block-pushing contest. The contestant randomly picks a stone block out of a huge pile of blocks of different sizes, and then a tireless slave will push the block down a lane (the slave is well-trained and always pushes the block with the same force). The contestant's job is to predict how far the block will slide before coming to rest. The contestant will win some amount of money based on how close his prediction was to the actual distance that the block traveled.
As far as I understand, Feyerabend is either saying that either a). Aristotle would win less money than Newton who would win less than Einstein, but we have no idea why, or that b). We can't know ahead of time who will win more money. Both options look disingenuous to me, but it's quite likely that I am misinterpreting Feyerabend's position. What do you think ?
If we imagine a test given by an Aristotelian physicist, defining impetus with the Newtonian definition of momentum would get no points (and vice versa). Feyerabend says
In other words, impetus is meant to explain, while momentum is something to be explained. The point is that it's very odd that two theories on the same subject disagree about what explains and what needs to be explained. (Imagine if one scientist proposed that cold caused ice, and the next generation of scientist proposed that ice caused cold, while making more accurate predictions). In the same way that impetus is a primary explanation for Aristotle, force is a primary explanation for Newton. And impetus and force are nothing alike. The assertion is that this type of difference is more than saying that Newton had better data than Aristotle.
In your hypothetical, I think that Feyerabend says something like (a). Perhaps "Aristotle would win less money than Newton who would win less than Einstein, but the naive scientific method cannot explain why." For some perspective, Feyerabend is opposing Ernest Nagel and logical positivism, which asserts that empirical statements are true by virtue of their correspondence with reality. If you believe Newtonian physics, the causal explanation "Impetus" doesn't correspond with any real thing (because momentum does not explain, but is to be explained). You could bit the bullet and accept that impetus is a false concept. But if you do that, then a theory based on lots of false concepts makes predictions in the block-push contest that do substantially better than chance. How can a false theory do that?
If that's what Feyerabend is saying, then he's confusing the map for the territory:
That would indeed be odd, but as I understand it, both theories are trying to explain why objects (such as stone blocks or planets) behave the way they do. Both "impetus" and "momentum" are features of the explanatory model that the scientist is putting together. Aristotle believed (according to my understanding of Feyerabend) that "impetus" was a real entity that we could reach out and touch, somehow; Newton simply used "momentum" as a shorthand for a bunch of math, and made no claim about its physical or spiritual existence. As it turns out, "impetus" (probably) does not have an independent existence, so Aristotle was wrong, but he could still make decent predictions, because the impetus's existence or lack thereof actually had no bearing on his calculations -- as long as he stuck to calculating the motion of planets or rocks. In the end, it's all about the rocks.
What is the "naive scientific method", in this case ? How is it different from the regular kind ?
No, you can't, since the existence of impetus as an independent entity is unfalsifiable (if I understand it correctly). The best you can do is say, "this impetus thing might exist or it might not, but we have no evidence that it does, so I'm going to pretend that it doesn't until some evidence shows up, which it never will, since the concept is unfalsifiable". Aristotle probably would not have said that, so that's another thing he got wrong.
The statements "ice causes cold" or "cold causes ice" are both falsifiable, I think, in which case the "ice causes cold" theory would make less accurate predictions. It might fail to account for different freezing temperatures of different materials, or for the fact that the temperature of a liquid will not decrease beyound a certain point until the entire volume of the liquid had frozen, etc.
I think that Feyerabend is mostly talking about maps, not territory. I shouldn't have said naive scientific method, because naive is unnecessarily snarky and I'm talking about a different basic philosophy of scientists than the scientific method. The basic "truth theory" of science is that we make models and by adding additional data, we can make more accurate models. But in some sense, the basic theory says that all models are "true."
That leaves the obvious question of how to define truth. "Makes accurate predictions" is one definition, but I think most scientists think that their models "describe" reality. The logical positivists tried to formalize this by saying that models (and statements in general) were true if they "corresponded" with reality. Note that this is different from falsifiability, which is basically a formal way of saying "stick your neck out." (i.e. the insight that if your theory can explain any occurrence, then it really can't explain anything) The Earth suddenly reversing the direction of its orbit would falsify impetus, momentum, relativity, and just about everything else human science knows or has ever thought it knew, but that doesn't tell us what is true.
For the logical positivist, when one says that "impetus does not have an independent existence" that means "impetus is false." There is some weirdness in a "false" theory making accurate predictions. To push on the map/territory metaphor slightly, if Columbus, Magellan, and Drake all came back with different maps of the world but all clearly got to the same places, we would be justified in thinking that there was something weird going on. Yet if you adopt the logical positivist definition of truth, that seems to be exactly what is happening. At the very least, the lesson is that we should be skeptical of the basic theory's explanation of what models are.
That is similar to my take on this.