Pratique du Shadowing: Philosophy of Science Lecture #2: Verificationism - Apprendre l'anglais à l'oral avec la vidéo
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Thank you.
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Thank you.
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A lot of people have felt that the distinguishing thing about science
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that makes it so special and cuts it off from other ways of examining the world is the method that science uses, some characteristic rigorous method
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that ensures the accuracy of its conclusions better at least than do the methods in other areas of inquiry.
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One very influential way of characterizing scientific method is in terms of its use of observation,
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especially experimental test.
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Now, while experiments are easier in some sciences than in others, nonetheless, the whole idea that theories should be testable,
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that theories should be observable, that has been extraordinarily influential in the history of science.
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Today, we're going to look at one popular and historically influential view about science's method called verificationism.
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The man who invented the name positivism in the middle of the 19th century was August Comte.
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It's spelled like August, except it's got an E on the end, just like the month.
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And his interest was to banish metaphysics.
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He thought that metaphysics had been the bane of all intellectual work that had gone before the 19th century,
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and that the developments of science in the 17th century and in the 18th century, and then also through the first part of the 19th century,
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had shown that the proper way to undertake an understanding of the world is science.
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And I guess he meant by that something like rigor.
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Now, he presumably had some sort of notion about what scientific method was since he meant to banish all other methods, calling them all metaphysical.
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But in particular, he thought that all theological modes of reasoning ought to be kicked out.
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These were misleading, led only to false conclusions, and hurt people.
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So what he hoped for was a new dedication of society to science.
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He believed on what we might now call sociological grounds that societies needed to have things like religions,
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and so what he wanted to do was to replace all the organized and standard religions with the worship, if you like, of science.
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Now that's sort of an interesting concept, I suppose.
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He also felt that all areas of inquiry should be radically reformed to reflect this scientific bias,
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or the scientific inclination, let's say.
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He wouldn't have said bias, I think.
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But that was his view, and positivism was widely regarded.
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Just because science had been so successful, it was almost a cult among intellectuals for a while, the whole notion of positivism.
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Again, meaning at that time, kicking out metaphysics, which was thought to be speculative and old.
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As a matter of fact, you get analyses from people.
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They talk about the religious mode of reasoning as being antiquated
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and sort of located in tribes and maybe in the dim and dark history of Western civilization.
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And then there's the metaphysical modes of reasoning.
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which are sort of philosophical, they're kind of superior to theological modes of reasoning,
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religious modes of reasoning, but the metaphysical modes of reasoning ought to be surpassed themselves by scientific modes of reasoning.
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So the new future of society is going to be scientific, as far as Comte and his followers were concerned.
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Now, his followers were not some small cult.
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Does the name Ernst Mach ring a bell?
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You nod yes.
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Who is he?
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He just rings a bell.
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Does anybody know who Ernst Mach is?
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He is a German scientist.
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Does anyone know in what field?
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Pardon?
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Physics, generally.
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Mechanics.
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He wrote a book called Die Mechanique.
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Why does the name Mach ring a bell?
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I'm sure that a lot of you don't know anything about the history of science.
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Mach 1, Mach 2, Mach 3.
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That's the speed of sound.
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Mach 1 is the speed of sound
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and his name is now attached to the measure for the speed of sound in an airplane to travel twice
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or three times, the speed of sound is said to travel at Mach 2 and Mach 3.
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And that label owes its name to Ernst Mach.
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He was a very influential German physicist, but he was a positivist.
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He thought that metaphysics should be banned.
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And what that meant to him, for example, in the 19th century, along with lots of other scientists who were right at the cutting edge of chemistry and physics,
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and who are building what we now call the atomic theory of matter.
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What that meant to them, to the positivists in that crowd, was that the atomic theory of matter should not be taken seriously as a characterization of reality.
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What they said about it, Ernst Mock in particular and other positivists among the physicists, was these are all clever calculation devices, if you like.
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These theories offer us a means.
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We're going to return to this later when we talk about instrumentalism in science.
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I just want to note this right here.
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He said we should not take seriously the idea that there really are atoms out there that make up molecules.
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These things are unobservable.
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You can't see them.
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Nonetheless, that doesn't mean we have to kick out the theory.
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The theory is a nice device for organizing data, if you like.
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It's a nice device for organizing data.
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It's sort of like a filing system.
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A theory allows us to assign certain variables to talk about, it's a language, it allows us to talk about phenomena in a certain way,
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but we shouldn't get metaphysical about it.
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We shouldn't think that just because the theory is useful in some way that there really are these things called atoms, I mean that would be ludicrous,
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and so that's the kind of attitude
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that i hope to characterize here is you know i want
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you to understand is instead of 19th century positive hoping for not
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and positive uh it's a sort of an unusual usage of the term
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but what they meant by the reason they were talking about positivism is
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because they were tired of what they took to be speculative
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uh attempts to explain nature what they wanted was down to earth
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verifiable that's the first time you've heard that word verifiable statements about the physical world.
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And when you start talking about things that are not observable, then you're talking about things that are not verifiable.
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You're starting to start getting spooky here, you're getting philosophical, metaphysical, and this is to be resistant.
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In the middle of the 19th century, it still probably seems that they had only very recently managed to free,
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to It will liberate science from the speculative character that it has had before the 17th century, say.
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And I think that a lot of them, when they started looking at theories like the atomic theory, which began to postulate these that you couldn't see,
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you couldn't taste, you couldn't feel, it sure did look like that old metaphysical stuff coming back in.
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It looked like impetus.
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It looked like natural places, the kinds of things that I mentioned Aristotle used to talk about that really didn't look scientifically.
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And so movement sprang up, the sort of vanity.
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That was 19th century positive.
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So positivism is to be equated with testability.
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What different positivists said And testability was the criterion of, that's going to vary from theory to theory.
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But what we're going to start off with is a hardcore version.
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And we're then going to go to a foster core version, positive version.
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Actually, we're going to, this is going to all be part of something called verification
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because there's another branch of positive version that we'll talk about next time.
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We'll talk about these today.
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So, next time we'll talk about falsification.
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It also expresses...
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the importance of tests, but in a different sort of way.
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Now, so positivism generally, all these theories we're going to discuss this time and next time,
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is marked by its emphasis on tests, on observability, at least observability in principle,
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and it's also positivism always emphasized the the deployment of tests in as experimental tests of theory
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and try to talk about the logic of the relationship between theory and tests now
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what goes what I'm calling the hardcore hardcore verification ism is associated with what with the verifiability criterion of meaning.
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And the verifiability criterion of meaning says quite plainly and simply, if something, you choose what?
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If proposition, sentence, theory, whatever, belief, if it's to have any meaning at all,
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it must be verifiable, right?
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Now, this is a very strong criterion.
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That's why I call it hardcore core.
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This is a criterion of meaningfulness.
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In other words, what they're saying is anything that's not verifiable, and they've got metaphysics in the back of their mind, they've got any theory like the atomic theory that,
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as far as you can tell, isn't verifiable.
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Now, it's open to question whether it is or it isn't, but Mach didn't think it was.
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It's certainly true.
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They're talking about all religious theories that talk about gods that can't be seen, heard, felt, tasted, or whatever.
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These are not just false.
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I mean, they're not even good enough to be false or true.
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They're meaningless.
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I mean, if you say, are there gods or not, what the hardcore verificationist is going to say is that question isn't even good enough to be true or false.
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I mean, I can't even tell you it's false.
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It's just a meaningless question.
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It's gibberish.
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It's garbage.
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It's not that you have to have verified it in fact.
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There are things that are going on outside the solar system
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or even on the dark side of the moon that you can make perfectly meaningful propositions about,
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according to the hardcore verificationists.
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You can make perfectly reasonable propositions about these things that are perfectly meaningful, provided that you have at least some idea of how one might verify it.
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It doesn't even have to be technologically possible, but if you can say, well, all right, what I mean by saying
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that there are things going on on the dark side of the moon is
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that if someone were there or if some mechanism were there that could make suitable recordings, it would record suitable things.
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You know, like it might take pictures, or it might make sounds, or it might record, if you're saying there's earthquakes on the dark side of the moon, even though there are no seismographs up there,
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all you have to do is be able to specify what
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sort of thing in principle would count as the kind of observation that would distinguish between the truth and falsity of that.
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All you have to do is be able to say, well, if we did have a seismograph up there, then what my sentence comes down to is that it would be registering something other than the norm.
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So all I mean is that you should, in order for the sentence to be meaningful, you should be able to specify what sort of thing would count as a verification of it,
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and what you assert when you assert the thing is that you would observe x if you had the suitable equipment.
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What this is just supposed to do is show that they're not being totally unreasonable when they try and banish metaphysics.
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They just want to banish things that don't make any difference.
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So that, for example, if I were to tell you that back there in that corner, everyone look, please, back there in that corner just below the clock is a six -foot -tall undetectable bunny.
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And I say it's undetectable.
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I mean it is absolutely undetectable.
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There's no way at all to detect that.
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There's no way to determine whether that's true or false.
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There's no way to verify it.
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Well, the positivist would say, well, it's all very nice.
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but, you know, if it's in principle unverifiable, it's meaningless.
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You've made no proposition whatsoever.
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Now, if I said you can't see it, but indeed here are some tests you could perform.
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I mean, you could put a carrot over here and it would be gone after 20 minutes.
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Verification would say, ah, well, maybe that's not so meaningless after all.
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At least you've offered us some potential observation that could be made that would tend to verify your assertion.
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But now, if we've got two propositions, two different propositions that would equally well explain the missing carrot,
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one of them, you know, the big six -foot -tall otherwise undetectable rabbit,
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two, maybe there's somebody that likes carrots and they're sitting over there nibbling in the back of the room,
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well, the positivist has some definite thoughts about which one we should prefer.
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It's the one that requires less of an extension of our normal testing procedures and requires less imagination and speculation.
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Gods, I think the hardcore verifications probably thought they'd banish most or all gods altogether by this criterion, but I suppose if there are some,
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you know, some people would claim that, no, I mean, you know, God is not somebody who, or something that is undetectable.
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I mean, you can see God's, you see evidence of God in all sorts of things.
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The verificationist wouldn't say that that's meaningless, but would point out that there are other ways of explaining, you know, would say that there are other ways of explaining the same things
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that God supposedly explains that do not require this extra hypothesis so that the hypotheses of physics,
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for example, and the physics plus evolutionary biology say,
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and the hypotheses of God are empirically equivalent if they explain the same data.
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And what we should do is to prefer the more parsimonious one.
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This is called Occam's razor.
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We should prefer the one that requires us to postulate fewer unusual, or in this case, supernatural sorts of things.
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Now, what it does banish is any divinity that is absolutely 100 % unverifiable, undetectable, unobservable.
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And what the verificationist wanted to say is not just,
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well, let's focus our attention here on a class of statements that are exceptionally interesting from the point of view of science,
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namely the ones that are observable or have observable consequences is they wanted to say,
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no proposition that is unverifiable is even meaningful.
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That was a very bold, it was anti -metaphysics.
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They want to say metaphysics is meaningless because unverifiable.
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And in a way, they defined metaphysics as that which is unverifiable.
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Remember what Mach says about atoms.
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He says, look, I mean, well, it might be a useful device for some purposes, but we shouldn't take seriously the idea that these things exist. And B .F.
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Skinner would say, this is quite apart from other things that Skinner might say, but he would say, there's nothing wrong with a mentalistic,
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to say that I have a feeling or that I have a mind, if you're just kind of informally speaking.
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He said, my mind tells me this, or I have a certain feeling.
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That's a perfectly decent expression, according to Skitter.
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But we don't have things called feelings that are somehow stored in there.
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No, we feel.
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It's an activity.
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It's a process.
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It's not a thing we have.
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And we've got to be careful about the implications of these modes of speaking.
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Well, this is precisely what the positives want to say.
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These modes of speaking might be very, very useful for certain purposes.
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But beware if you suddenly become committed to little things called atoms or electrons or quarks.
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I mean, you can't see these things.
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You can't even in principle see these things.
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The argument about whether atoms even had structure is, you know, centuries old.
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And the argument about whether electricity is to be understood as a particle -like
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or wave -like phenomenon is still kind of weird to this day.
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So whether these little things called particles, the electron is supposed to be the particle that bears the negative electric charge,
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it's still kind of dubious how you're supposed to talk about those things.
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There's a nice mathematical language, but what English words to use to describe these phenomena is not at all clear.
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And what the positivists in any era would say is these mathematical languages do not abandon them.
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But remember, they're just notation devices.
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They're calculation devices.
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They help us get from data to data.
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We've got some input data.
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We plug them into our equations.
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And these equations allow us to make accurate predictions about what observables.
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And that's all that counts is that we're able to make accurate predictions about what will happen in an experimental setting.
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So you might want to say, we observe an electron.
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It doesn't matter.
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Forget about the electron.
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The electron is just a convenient device to predict
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that under certain circumstances we will hear a click on
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that Geiger counter or that we will see a cloud trace in
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that Wilson cloud chamber or that we will get a certain result on the oil drop experiment.
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That's what's really going on here, according to the positivists.
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Our theories are mere calculation devices.
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We shouldn't take them seriously as talking about things in the external world.
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And the criterion for meaningfulness is verifiability.
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If a sentence or proposition, whether scientific or not, if it's not verifiable,
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If there's no way that you can even say how we should go about demonstrating the proposition to be true, well then, it's not meaningful.
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And I want to return to the remark made up there, and then we'll get into another brand of verificationism, the soft core, because it was the hardcore verificationists,
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to their credit, that one day opened up their eyes and said, whoop.
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They said, uh -oh.
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And it involved the verificationist criterion of meaning itself.
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The verifiability criterion of meaning says what?
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It says a proposition is meaningful only if it is verifiable, otherwise meaningless.
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Now, what kind of thing would it be to verify that?
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I mean, how would you demonstrate it to be true?
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It's not the sort of thing that you could demonstrate to be true.
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It's sort of like a suggested norm.
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It's saying, what it says tacitly is, we should no longer take seriously things.
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It's a should statement, right?
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It says we should steer clear of metaphysics.
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We should not take seriously any metaphysical propositions.
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We should only attend to verifiable propositions.
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It's a norm.
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It's not verifiable.
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Well, if not verifiable, then what on the verifiability criterion of meaning?
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Gibberish.
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Meaningless gibberish.
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So they said, whoop, and they fell back with a variety of different sorts of reactions.
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Fell back to the soft core position, which involves not a verifiability criterion of meaning,
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but instead the verifiability criterion of demarcation.
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Those words we're going to have to talk about, and we will.
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But first, one more question.
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Yes?
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What if you had a theory that was not verifiable at a present time?
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If you mean is not verifiable because we lack the technology,
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then that doesn't stand in the way of its being meaningful even on the hardcore theory, even on the verifiability criteria of meaning.
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All that's required is that there be some way in principle, not in fact, that you could specify,
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like, for example, having a seismograph on the dark side of the moon, something that you could explain what you meant,
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what you would expect to find out if you performed the relevant tests.
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Tell us what the relevant tests would be.
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Like you could say, I think there's a giant zebra behind Pluto
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that always stays back there and we can never see it.
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That can be as meaningful as you please.
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I mean, false in their view, but that's as meaningful as you please if what you mean is, well, if we had a spaceship and went around back there, there'd be this big, giant zebra.
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I mean, if that's what you, that's fine.
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That makes it meaningful.
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The problem is when you say, I think there are some things that are just absolutely undetectable.
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They'll say, well, think away, but what could you possibly be talking about?
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What could you possibly mean?
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in saying that there are things that couldn't possibly be detected by sight,
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sound, any means, no machinery, no mechanism could possibly detect it?
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What could you possibly mean?
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I don't know how close this is or not.
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Just in saying that, it struck me as bearing a resemblance to the following thesis, which I think is at least plausible.
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And that's that there's nothing you could say that doesn't try to,
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no description that you can offer that doesn't try to bring the thing described under known categories.
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Like if I try to describe something that's strange or unusual, I will try and tell you what it's like.
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And what I'm doing there is trying to show you what sort of thing to expect, even though I'm telling you it's strange and unusual, it's different.
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It's kind of like this in that respect.
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It's kind of like that in the other respect.
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I think what the verificationists were grappling with was something like that idea, except they wanted to make it a little bit, they wanted to pin it down a little bit better than that.
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So what they said was, you need to specify not just what kind of thing it is,
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but to specify which steps you'd have to take in order to test what you just said.
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That will establish what it means.
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Now then, to perform the tests, we'll decide whether the sentence is true or false.
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Like what the sentence, according to the verification, the hardcore ones, what the sentence about
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that zebra floating out there in space means has something to do with what sorts of things would happen
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if you were on a ship out there, an observing probe out there.
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To specify which readings you'll get, what images you'll get, what pictures you'll get,
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that exhausts the meaning of the sentence.
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You will see something with stripes rather than something without stripes.
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That's why we say it's a zebra.
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That's what it means to say it's a zebra.
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It will look sort of horse -like.
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That's what it means to say.
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That's another part of saying it's a zebra rather than a skunk.
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And it will be very, very large, much larger than the normal horse.
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That's what it means to say it's a giant, right?
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Et cetera, et cetera.
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And the way we flesh out, for the hardcore verificationist, the way we flesh out the meaning of any sentence at all, it doesn't have to be scientific,
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is in terms of what would happen if we did that.
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That's operationalizing it.
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That shows you how you would perform, how you would investigate it, and what you would expect to get.
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Now, let's get in a ship and go out there on the other side of Pluto and look, hot -nosed zebra.
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Now, sentence turns out to be false, but it can't even be false or true until it is meaningful, unless it's meaningful.
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Again, the simple question was, what about stuff we can't now verify, but we manage to verify it later?
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No problem.
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It's meaningful all the way through, as long as you could say what sort of things would have to be done to verify it, even though we can't.
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An example, a case in point, and this is the sort of thing that the verificationists, whether hardcore or softcore, love of.
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Albert Einstein proposed the general theory of relativity in 1916.
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It's an extraordinarily abstract and difficult theory.
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And it was proposed not in order to explain any known anomalies
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or problems or any kinds of experiments that no one could explain.
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That wasn't the problem at all.
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The reason it was proposed is to offer a better organization or synthesis of physics.
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I'll try and explain that a little later.
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So right then in 1916, when it was proposed, there weren't any experiments that were especially well confirmed by that.
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And Einstein and others who were sort of interested in theory had to try
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and think of what kind of experiment could be performed that would verify the theory.
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And it wasn't real easy to do.
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Einstein himself thought up of at least one, and I don't know whether he thought up the other two, but for the longest time, right up into the 50s,
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I think, there were only about three known ways to verify the theory.
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And in 1916 in particular, the one way that seemed likely to be easiest to verify, it couldn't be done for practical reasons.
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There was a war going on.
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So it wasn't until 1919 that the observation was performed.
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And when it was performed, it seemed to verify the general theory of relativity.
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But in those intervening years, the theory wasn't meaningless, according to positivists.
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It's just that Einstein had proposed how to test the theory, thereby establishing its meaningfulness.
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He said, if you perform such and such an experiment, if my theory is right, you'll see this.
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If my theory is wrong, you should see that.
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And that's sufficient to establish its meaningfulness, even though the tests had not yet been performed.
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But of course, we've got a problem.
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Let us see what they did.
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I've suggested that what they've done is to go from the hardcore verifiability or verificationism to soft -core verificationism.
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And in this, they adopt, rather than a criterion of meaning, a criterion of demarcation.
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Now, the whole idea of a criterion of demarcation was actually introduced, I mean, that expression, criterion of demarcation, was actually introduced later by Karl Popper,
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who we're going to talk about next time.
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But the general idea is this.
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What we want to know is what's the difference between science and non -science?
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What is the demarcation line?
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What divides science from pseudoscience?
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The way Popper explained it, or actually I should be careful here.
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His student, Imre Lakatos, explained it this way.
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He was telling this story about Popper.
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Now I'm taking Lakatos to know what Popper went through.
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But the idea was this.
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Back in the teens, 1916, 17, 18, 19, 20, when Popper was going to school in Vienna,
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Vienna was an extraordinarily booming place.
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I mean, everything was going on there.
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First of all, it just left the Austro -Hungarian Empire, which was just on the verge of collapse because of World War II,
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but it had been collapsing for some time, probably for 15 years.
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The war will be the end of it.
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So in much the same way as the Soviet Empire is collapsing right now, at that particular time, the Austro -Hungarian Empire was collapsing.
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Now, what's interesting is that as the Austro -Hungarian Empire collapsed, an empire
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which had preached the evils of socialism for all of its
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days since Karl Marx had written in the middle of the century,
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the fact that the powers were collapsing meant that everyone felt free to move into this previously forbidden area.
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Karl Marx's scientific socialism, his scientific approach to why it is that societies change.
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They change because of the changing material conditions of production.
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They change because, in the end, of economic forces that are out of the control of revolutionaries, out of the control of state leaders.
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They just are facts that leaders and ideologues will just have to deal with.
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I mean, Marx was extraordinarily impatient with ideology and revolutionaries who would try to inflict ideology on history.
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History guides itself by facts.
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And so this was scientific socialism, and this was just all the rage in Vienna.
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At the same time, there was new architecture that was springing up in Vienna, new art forms, brand new sorts of music.
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Freud, Sigmund Freud was in Vienna, and physics was in Vienna.
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I mean, some of the great discoveries were going on in Berlin, but it was in Central Europe in Germany and in Austria,
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where some of the great work was being done in physics in those years.
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And Popper was being educated at that time.
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And so Popper said to himself,
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how is it that I am not as impressed with such supposedly scientific theories as Marx's or Freud's,
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for that matter, as I am with Einstein's?
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I mean, just to take an example, here are several, I mean, what Freud was doing, for example,
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was offering what was billed at the time as the first scientific theory,
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first scientific interpretation of human behavior, of human psychology.
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And so all the intellectuals were flocking.
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And again, there's this influence of positivism that says everything scientific is good.
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And so what Popper says is, well, I do like science, but what is it that makes me suspicious about these things like Marxism and its claim to be scientific,
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or Freudianism and its claim to be scientific?
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And while at the same time I seem to find that I'm a believer in the scientific character anyway, of the general theory of relativity.
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Even though it hasn't been tested yet, it's plainly a scientific theory.
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And even though it may be wrong, it's clearly a scientific theory.
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So he's not talking about what's right and what's wrong.
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He even said, you know, he was kind of sympathetic to Marxism.
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He was sympathetic to Freudianism.
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But he did not think of them as scientific theories.
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What's the difference?
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How come Darwinian or Mendelian genetics and Darwinian evolutionary theory, how come they seemed scientific, he wanted to know.
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But these other things don't.
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What is the criterion I'm using?
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There's some criterion I'm using to distinguish science from pseudoscience, to put it baldly.
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Now, Popper's the one that, now that was when he was in school, and later in the 30s, he offered an alternative to the verifiability criterion of demarcation that we're going to discuss now.
390
But the verifiability criterion of demarcation goes like this.
391
It says, verifiability is not the necessary condition of meaningfulness.
392
Things can be meaningful even though they're not verifiable, like, for example, this sentence, that very sentence.
393
Things can be meaningful even though they're not verifiable.
394
However, in order to be scientific, ethic, a sentence must be verifiable.
395
Scientists, said the soft core verificationists,
396
scientists are concerned only with propositions,
397
sentences, beliefs, assertions that are in principle verifiable, etc., etc., etc. So it's a softening of the position.
398
It's no longer a criterion of meaningfulness, it's a criterion of demarcation.
399
And it's here that they would point to theories that are extraordinarily abstract,
400
like Einstein's, and explain what the difference is between Einstein's theory of general relativity,
401
for example, and some other theory like, well, any arbitrary philosophical theory, Plato's theory of forms, say,
402
which you may or may not know about, or Descartes' theory about mind and matter,
403
the bifurcation of the human being into a material and the mental realm.
404
The soft core verification has said the problem with those theories is not that they're meaningless, it's the fact that they're not verifiable,
405
there's nothing you could do to verify one of those theories, just shows that it's not scientific.
406
And so if you're, you know, if you want to do metaphysics, that's fine.
407
It wasn't for the hard core verification.
408
It's the soft core verification.
409
Well, you know, if you want to do metaphysics, that's okay.
410
It might even be useful, helpful, illuminating in some way, but it's not science.
411
If you want to get down to science, then that's when we should stick to these verifiable propositions.
412
Take, for example, Einstein's general theory of relativity.
413
Now, the point, the reason that Einstein was moved to seek
414
and to try to work out the general theory of relativity was because of a fact about the special theory of relativity.
415
It was incomplete.
416
I mean, he knew it was incomplete at the time.
417
What he was trying to do was to formulate the laws of physics.
418
This is what he was trying to do in the special theory of relativity so that they would remain the same.
419
He would get the same formulation of the laws of physics,
420
whether you were on an object that was stationary or whether it was in motion with respect to some arbitrary reference frame.
421
He'd wanted to sort of simplify the laws of physics
422
so they would come out the same from any so -called inertial frame of reference,
423
that is, frames of reference that were either at rest with respect to one another or in uniform motion,
424
uniformly motion with respect to one another.
425
Not, in particular, the special theory of relativity did not formulate the laws of physics in such a way
426
so that they would come out the same on an object that was accelerating with respect to another frame of reference.
427
So that, for example, the laws of physics would have to be formulated differently on an object that was rotating another object, like the Earth around the Sun,
428
than it would from the point of view of the Sun.
429
Now, this was an embarrassment.
430
I mean, not an embarrassment, but this was an incompleteness in the special theory of relativity that needed correcting.
431
And so what Einstein spent time doing is trying to figure out just how to reformulate the laws of physics
432
so that they were completely general.
433
so that they would appear to be the same no matter whether you were on a, you know, just take an arbitrary frame of reference like the center of the sun,
434
they would be completely the same whether you were at the center of the sun, of course you'd be pretty warm there, or whether you were at rest with respect to the center of the sun,
435
or whether you were moving in uniform linear velocity with respect to the sun, or whether you were accelerating toward the sun, or accelerating the way from the sun, or orbiting the sun.
436
He wanted perfectly general laws of physics, laws of motion especially, that could be formulated so that they would come out the same for all those perspectives.
437
Now, that was his reason.
438
It was a systematic reason.
439
That was his main reason for trying to figure out the general theory of relativity.
440
Oh, I'm sorry.
441
Okay, so his reasons didn't have anything to do with trying to explain the perihelion of mercury,
442
nor were there any other phenomena that he was trying to accommodate in going from the special theory to the general theory.
443
Indeed, he was always mostly a systematic thinker and a generalist, very abstract.
444
Okay, so anyway, he formulates the theory.
445
It's all abstract work, all looks philosophical.
446
I mean, this is why it's a neat test case, because his reasons were abstract, didn't have anything to do with experiments or observables.
447
The theory that came out was extraordinarily abstract and looked really strange.
448
Really, really strange.
449
Let me give you an example of its strangeness.
450
In the normal course of things, we're taught Euclidean geometry.
451
And among the axioms of Euclidean geometry is this one.
452
Here is a, let's say the surface I'm drawing on is a Euclidean plane.
453
And the axiom goes like this.
454
If you've got a line in that plane and then there's a point off that line, but still on the plane,
455
then there is one and only one line that you can draw through that point parallel to that line in that plane.
456
Now, that's a lot of words, right?
457
It's a complex axiom to state, but if I stated it well enough, it should be obvious to you.
458
Does it seem obvious that, of course, that's true, that there's one and only one line parallel to that line through that point?
459
Not for Carl.
460
Well, okay.
461
But in any case, that is the fifth Euclidean axiom.
462
Now, it is so clumsy to say that for centuries, you know, because Euclid figured, Euclid was a student of Plato's, or I'm sorry, Aristotle was a student of Plato's and Euclid was a student of Aristotle.
463
So this is an old system, Euclidean geometry.
464
It's so clumsy that for centuries, people were trying to figure out whether they could possibly derive this one from the other four, which were much more simple.
465
And if they could just have a system of four axioms and not this clumsy one, that would be so nice.
466
Well, they never were able to do it, but part of that effort in the 19th century went this way.
467
A lot of people like a man named Riemann, a mathematician named, there's others.
468
Riemann is foremost among them.
469
Lobachevsky comes later.
470
He's another geometer.
471
But just to see if they could prove that this axiom,
472
this fifth one, was deducible from the others, they said, let's go in the back door.
473
Let's try an indirect proof.
474
Equals fifth.
475
Let's try an indirect proof.
476
Let's assume that it's wrong.
477
Let's pretend we can have, let's just say, we can't make sense of this, Let's say we can have two,
478
or three, or four, or even an infinite number of parallel lines through that point in that plane, to that line, et cetera.
479
Let's just assume the contrary.
480
Let's start out with two.
481
Now, we can't picture that, right?
482
That doesn't make any sense to picture, but let's just say it, and let's see if we can derive a contradiction with the other four.
483
Well, they worked, and they worked, and they worked, and not only did they not derive a contradiction, they proved that they couldn't derive a contradiction,
484
and instead, they they produced a perfectly consistent non -Euclidean geometry
485
that just had this new axiom placed in there instead of the old one.
486
And in addition, they then went on to try some other theories, and they got other non -Euclidean geometries.
487
Well, what general relativity theory says, now those were just sort of mathematicians' delights back then in the 19th century,
488
but what general relativity theory says is our universe is not Euclidean.
489
The physical theory that we believe now about the physical universe says it is not Euclidean.
490
But it's not any one of these others, either.
491
What it is is something that varies.
492
The very structure of geometry, the geometrical structure of space -time changes as you move from
493
place to place in the universe as a function of the concentrations of mass.
494
If you get real close to something with a lot of mass, like a star or a sun, the geometry of space changes.
495
The whole picture, the geometry of space changes, And it's very different there or near a black hole, which is even worse.
496
We haven't confirmed that definitely, but it certainly seems like a good theory and it works well with lots of other things.
497
Near a black hole, the geometry of space -time is even more perturbed, more disturbed.
498
And the differences between those places, which are near concentrations of mass, and places that are in relatively free space,
499
the differences in geometry are massive.
500
They're big, big differences.
501
Now, it's that fact that the general theory of relativity predicts that the geometry of space,
502
space -time actually, the geometry of space -time alters in the presence of massive objects.
503
That's the key to Einstein's bright idea about how to test his theory.
504
This is supposed to be a good illustration of the verifiability criterion demarcation.
505
This is supposed to show just the sort of thing that makes Einstein's speculative abstract endeavor a scientific one, as opposed to the equally abstract,
506
equally difficult intellectual endeavors conducted by the philosophers like Plato and the others.
507
Einstein's is different and scientific because verifiable, and it's this key fact about the geometry of space -time,
508
curiously enough, that turns out to be the key to figuring out how to perform a verification,
509
figure out what kinds of steps would be taken to show that his theory is true.
510
The verifiability criterion of demarcation offered by what I've called the soft core
511
verificationists seem to many to really capture the very special feature about science that made it so successful.
512
But as we'll see, even it came under rather or heavy fire, and this for logical reasons.
513
¶¶ Thank
514
you.
515
Thank you.
516
Thank you.
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Vocabulaire et conseils d’expression pour cette leçon
Cette vidéo contient 516 phrases et 6737 mots à répéter en shadowing. La partie parlée dure 45:57. Le locuteur parle à un rythme régulier d’environ 147 mots par minute, confortable pour le shadowing. 83 % des mots font partie des 3 000 mots les plus courants en anglais ; le reste mérite d’être vu avant de commencer.
Vocabulaire clé de cette vidéo
15 mots de la vidéo à retenir, avec leur prononciation et leur sens :
| Mot | Prononciation | Sens |
|---|---|---|
| meaningful adjectif | /ˈmiː.nɪŋ.fl̩/ | significatif, qui a du sens |
| physics nom | /ˈfɪz.ɪks/ | physique |
| verify verbe | /ˈvɛɹɪfaɪ/ | vérifier |
| geometry nom | /d͡ʒiˈɑ.mə.tɹi/ | géométrie |
| meaningless adjectif | /ˈmiː.nɪŋ.ləs/ | dénué de sens, dépourvu de sens |
| verification nom | /ˌvɛ.ɹə.fɪˈkeɪ.ʃən/ | vérification |
| abstract nom | /ˈæbˌstɹækt/ | résumé |
| experiment nom | /ɪkˈspɛɹ.ə.mənt/ | expérience |
| principle nom | /ˈpɹɪn.sɪ.pəl/ | principe |
| proposition nom | /ˌpɹɑpəˈzɪʃən/ | proposition |
| specify verbe | /ˈspɛs.əˌfaɪ/ | spécifier |
| atom nom | /ˈætəm/ | atome |
| unusual adjectif | /ʌnˈjuːʒ(u)əl/ | inhabituel, insolite |
| observation nom | /ˌɑbzɚˈveɪʃn̩/ | observation |
| phenomenon nom | /fəˈnɒm.ɪ.nən/ | phénomène |
Les verbes à particule que vous entendrez
| Mot | Prononciation | Sens |
|---|---|---|
| figure out verbe | cerner | |
| come out verbe | /ˌkʌm ˈaʊt/ | sortir |
| kick out verbe | foutre dehors, mettre à la porte | |
| make up verbe | /ˌmeɪk ˈʌp/ | constituer, composer |
| find out verbe | découvrir, savoir | |
| go out verbe | sortir | |
| go through verbe | traverser | |
| open up verbe | ouvrir |
La grammaire de cette vidéo
Les structures que le locuteur utilise le plus, avec les mots exacts de la vidéo :
| Structure | Dans la vidéo |
|---|---|
| Phrases conditionnelles if + proposition, will/would + verbe — une condition et son résultat | if my theory is right, you'll see |
| Present perfect have/has + participe passé — une action passée qui compte encore maintenant | have felt · has been · you've heard |
| Voix passive be + participe passé — l’accent est mis sur ce qui arrive, pas sur qui le fait | be kicked · was thought · being antiquated |
| Propositions relatives who / which + proposition — une précision sur une personne ou une chose | man who invented · metaphysics, which was · that which is |
Prononciation à surveiller
Le locuteur utilise 125 contractions et formes réduites, comme they're, can't, I'm. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Les sons « th »: mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, nonetheless /ˌnʌnðəˈlɛs/, sympathetic /ˌsɪm.pəˈθɛt.ɪk/, theological /θi.əˈlɑd͡ʒɪkl/, altogether /ɔl.tuˈɡɛð.ɚ/
- Les sons « sh » et « zh »: verification /ˌvɛ.ɹə.fɪˈkeɪ.ʃən/, proposition /ˌpɹɑpəˈzɪʃən/, unusual /ʌnˈjuːʒ(u)əl/, observation /ˌɑbzɚˈveɪʃn̩/, influential /ɪnflʊˈɛnʃəl/
- Mots longs — placez bien l’accent: geometry /d͡ʒiˈɑ.mə.tɹi/, verification /ˌvɛ.ɹə.fɪˈkeɪ.ʃən/, experiment /ɪkˈspɛɹ.ə.mənt/, proposition /ˌpɹɑpəˈzɪʃən/, unusual /ʌnˈjuːʒ(u)əl/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Répétez phrase par phrase à vitesse normale, en reprenant chacune jusqu’à ce que votre rythme corresponde à celui du locuteur.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme meaningful, physics, verify.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.