A.J. Ayer and Logical Positivism

Logical positivism, this was a movement of philosophy that flourished in the first half of the 20th century. Primarily, it originated in Austria.

Um, there was a famous group of philosophers who, uh, used to meet in the 30s, uh, early 30s, in Austria, specifically Vienna. That included such people as Moritz Schlick, who was, uh, the person who sort of ran it, uh, Otto Neurath, Hans Hahn, and Rudolf Carnap, among others. Other people sat in, um, who, uh, for example, Karl Popper, who we'll be meeting later, who was a very influential philosopher of science. Who, uh, I've got him listed under "Frenemies" because he was, uh, in some respects, he's sympathetic to what's going on with the, um, with the logical positivists. He shares common enemies. Both logical positivists and, and Popper are critical of people like, uh, Hegel and, um, Marx as a scientist, not necessarily Marx as a social theorist, um, and Heidegger, for example. Uh, but also Popper has a problem with a key tenet, perhaps the key tenet of logical positivism, which we'll be looking at in more detail in a second, which A.J. Ayer talks about.

Yes, so Ayer is the English representative. He sat in in the Vienna Circle as a very young man. Him, both he and Quine were very young attenders of the, um, meetings of the Vienna Circle. The Vienna Circle disbanded as the 30s went on because a lot of them were Jewish, and all of them were intellectuals, and Nazism was on the rise. Moritz Schlick stayed behind and died. Um, he was shot by a former pupil. Um, and some people say the former pupil was just crazy, you know, like Mark David Chapman shooting John Lennon. Uh, other people are convinced that Schlick was shot because of the Nazis, that the Nazis wanted him dead. So there's a philosophy conspiracy theory for you right there. But anyway, Schlick was an early leader and, and died. Um, his life was cut short by a bullet, which is unusual for philosophers. Thankfully, people like Rudolf Carnap, was perhaps the, uh, longest lived, well, the person who had the longest influence because he moved over to America and settled in. And he and Quine had sort of an ongoing exchange. Um, and Quine did his best to continue and sort of modify the tenets of logical positivism, um, in the face of, uh, serious criticisms. In general, logical positivism is seen to be a movement that flourished, that burned brightly, and then was swept away. Uh, there's nobody nowadays who claims to be a logical positivist. There are certainly people who think stuff that Carnap said is right, uh, but they sort of changed their name. They, they ceased to be labeled as logical positivists. They're just sort of empiricists. Uh, but it had lasting effects. Even though it sort of didn't last very long, it had lasting effects in that it was a very radical movement that aimed to sort of sweep away a lot of what counted as philosophy, and it did that. Um, it had a huge influence, uh, not just in the German-speaking world, but because the Vienna Circle, because of people like A.J. Ayer who sat in, and because the members of the Vienna Circle went to, to England and America to escape the Nazis and became important figures there, it had huge influence in the English-speaking world. And it was like, you know, punk in music. The logical positivists, the punks of philosophy, in that they sort of rubbished what came before and had very strict rules for what counted as philosophy. And this had a sort of chilling effect on some parts of philosophy that they deemed unworthy, uh, for quite a while. And it was basically the 70s before the influence had really worn off and, and work had sort of tended to blossom again in, in fields that they were critical of.

Okay, so we're going to, uh, well, yes, I should say a bit about their concerns. Um, perhaps their major historical influence is Hume. And, um, Hume makes a distinction that they thoroughly endorse between, well, they don't use his language, his language is between "relations of ideas" and "matters of fact." Uh, Hume says, these are two types of truth. Relations of ideas are the contentful ones where, and no, I'm sorry, relations of ideas are what we now call analytic claims, that is, something like "Hesperus is Hesperus," where it's true, but its truth does not depend on any facts about the world. Its truth depends on just rules of language. "Hesperus is Hesperus" cannot possibly be false because of the meanings of the words. Now, consequently, analytic truths don't really tell us anything. They're just sort of true by definition. And, um, so to, they are, they do count as meaningful and true, but in some sense, they're a lesser kind of truth. And it's worrisome that, for example, the logical positivists counted all of the claims of math as analytic, and we'll get to that as a criticism, um, in a little bit. Uh, but the interesting stuff is the matters of fact, according to Hume, or synthetic truths, according to, uh, later terminology. This is what science, uh, is interested in. These are, um, actual, informative claims about the world that are discoveries, that are news, that aren't just true by definition. They're true, but they could have been false. So it's interesting to discover that they are, in fact, true. Um, now, Hume said, uh, all truths can be divided into these two. Anything that doesn't fall into these two, he had, this is one of the most famous passages in philosophy. It's, um, it's Hume writing. I can't remember if this is the *Treatise* or the *Enquiry*, but he says, "When we run over libraries, persuaded of these principles that, uh, truths are divided into these two camps, what havoc must we make if we take in our hand any volume of divinity or school metaphysics?" School metaphysics was the kind of philosophy, uh, that was in vogue in the Middle Ages, that the early modern philosophers like, uh, Descartes, Locke, Hume, Leibniz, Spinoza, kind of swept away. It was basically working on the principles that Aristotle had laid down and making very fine distinctions. It's basically footnotes to Aristotle. Early modern philosophy came along and said, "Forget that stuff." So, um, "if we take in our hand any a volume of divinity or school metaphysics, for instance, let us ask, does it contain an abstract reasoning concerning quantity or number?" That would be, um, relations of ideas, so that's one of the two categories. "No, does it contain any experimental reasoning concerning matter of fact and existence?" That's the other category, matters of fact or synthetic truths. "No." So if it doesn't, so in other words, it doesn't fall into any of the either of the two groups that count, "what do we do then? Commit it then to the flames, for it can contain nothing but sophistry and illusion." So this is very radical. It's now, Hume is speaking kind of metaphorically, but, you know, there's there's steel in behind his words. He's saying there's all of this that philosophers churn out, the philosophers and theologians churn out, claiming to be meaningful and deep, but there's a simple test that you can do. Run it, run, uh, my test on, on what they're saying, and if it fails the test, that basically means it's, it's empty, it's meaningless, and you can burn it with no loss to humankind. That is almost exactly what the, uh, positivists are recommending with their verification principle. Um, so Hume is a very important influence. Um, also more recent influences before the positivists are Frege and Russell, and the early Wittgenstein. The early Wittgenstein actually sat, was one of the people who visited the, uh, Vienna Circle.

The early Wittgenstein, he was, he was, uh, an architect, I think, training to be an architect, um, at the time. Wittgenstein is, Wittgenstein is kind of a cult figure. We'll talk about Wittgenstein in more detail. The big thing about Wittgenstein is that he has two stages, at least two stages, but two clearly distinct stages in his philosophy. There's the early Wittgenstein, where he's influenced by Frege and Russell. He meets Frege. Frege tells him, "You're smart, go work with Russell." He goes to work with Russell, and then he produces this work called the *Tractatus*. Um, while he's fighting in World War I, on the wrong side, I might add, um, he produces this work called the *Tractatus*, which is notoriously hard. It's very austere, it's very curt. It's structured in this weird way where there's sort of seven, uh, basic principles, and then there are sort of footnotes to them. Um, uh, one of my professors, uh, in the early days of the internet, suggested it would make a great hypertext. In other words, you just start with the seven principles and you click on them, and it would take you to the others. So it has this structure, and it's very, as I said, it's very curt. Uh, there are quotes from it in one of the readings that I gave you, from the Miller book of philosophy of language. It starts with quotes from the *Tractatus*, and they say things like, "To understand a proposition means to know what is the case if it is true." That's one of the more understandable and clear-cut statements of it. Uh, but it's basically presenting a picture that is in keeping with, with the Frege-Russell project of, you know, logic is clear and unambiguous, and it's informative in that it tells us something about the world. Uh, the, uh, the logical positivists really liked that. And actually, the logical positivists are very much, if they're influenced by anything more than, more than anything else, it's the progress that science is making at the time. You know, this is the time of Einstein, so science is making huge advances in our understanding of the world. And the logical positivists sort of look at the way science is exploding and compare it with philosophy, which at the time was very much influenced by Hegel. In the same way that at the time of the early modern, you had sort of Aristotle looming over everything and, and, you know, he was, uh, all respectable philosophy was just talking about Aristotle. It wasn't entirely that way with Hegel, but certainly in the German-speaking world, Hegel was an undue influence. And actually, Hegel had an influence on, uh, British philosophy in this guy over this guy called F.H. Bradley, who's a 19th-century Hegelian who taught, uh, some of the early figures. He taught G.E. Moore, for example, who was a contemporary of Russell's and considered, uh, along with Russell, the founder of analytic philosophy. Analytic philosophy has a lot in common with logical positivism. It's very much committed to the idea that you've got to be clear and you've got to say something.

Quine, also very much, uh, interested in science, uh, very much in the positivist camp, that science is doing the important work and philosophy should be influenced by science, but has some key differences with the positivists. And writes a famous article that is also hard to read. Quine writes beautifully, but doesn't write very clearly. It's, it's almost like he's committed to style over substance. Uh, but the, the sort of landmark article that kind of put the boot into logical positivism by Quine is called "Two Dogmas of Empiricism," and it actually attacks this key distinction of Hume's between "relations of ideas" and "matters of fact," between analytic and synthetic, and claims that you can't support that key distinction. And if you can't, that undermines basically a lot of the logical positivist project.

Let's see. Uh, okay. So one of the things that Moritz Schlick says famously is, "The meaning of a proposition is its method of verification." Now, this is actually saying something slightly different from what, uh, Ayer says in the reading, which is the reading that we did for Ayer is "The Elimination of Metaphysics," which is chapter one of his book *Language, Truth and Logic*. This was actually a lot like Hume. Hume's, uh, *Treatise* was written when Hume was in his early 20s, and it's like one of the masterpieces of philosophy, and he wrote it, you know, when he was but a, a, a lad. And it's seen as, you know, he was this prodigy. A very much influenced by Hume, Ayer writes *Language, Truth and Logic* when he's in his early 20s, so he's seen as this prodigy. Um, Hume, Hume's *Treatise* fell stillborn from the press, as he put it, at the time. Didn't seem to catch on with many people. So he rewrote it as the *Treatise* divided into two sections, rewrote it in a more accessible fashion, as he thought. That failed too. So he quit and went into writing history and wrote one of the most, the bestselling, uh, works of English history ever written. So he was all right. But, uh, and it was only later, after he died, when Kant read Hume, that, uh, the true importance of Hume's work, uh, really sank in. And Kant, the fact that Hume was a huge influence on Kant, even though they disagreed. Kant famously said, "Hume awoke me from my dogmatic slumber." That's when Hume kind of took off and became, uh, as famous for his philosophy as he was through his history.

Ayer wrote this work, *Language, Truth and Logic*, and that was kind of the big thing that he did in his philosophical life. He continued to be a respected philosopher in, um, in Britain. I think he was at Oxford. I want to say. I should know. Um, you know, and lived a long life. He actually, everybody called him Freddy. So the A.J. must be for Alfred. Uh, and, uh, actually, there's a, there's a story about the time A.J. Ayer almost got into a fight with Mike Tyson. So he, uh, he clashed with celebrities. Look that one up. He would have been murdered. He was not a big guy, but he was a feisty guy, put it that way. All right. So Ayer writes this work, *Language, Truth and Logic*, which is seen as sort of a, um, a polemic of the, the, um, a manifesto, if you will, of the Lo of logical positivism. It's not, I mean, not all logical positivists would agree with everything it said, and it seems to be sort of the more extreme version of logical positivism. But it has the great virtue of being clear, of being clear and being bold. Um, so, so people love it for that. And certainly this first chapter is called "The Elimination of Metaphysics." So metaphysics is this big area of philosophy where we talk about things that science can't talk about, like free will, like, uh, the basic, uh, substances of the universe, not substance in the way that science talks about, but substance as in, is mind a substance? Is matter? You know, the ancient Greeks were interested in metaphysics when they talked about, is matter composed of earth, air, fire, and water? The elimination of metaphysics means getting rid of this stuff that's been talked about for 2,000 years and just basically saying, yeah, that stuff that you, all of you great philosophers were talking about for over two millennia, that's all, you know, pretty radical stuff. And, uh, the way that we eliminate it is very similar to what Hume suggested. There's the verification principle, which, um, uh, he calls the "criterion of verifiability." We say that a sentence is factually significant, uh, to any given person. So notice first of all, this verification, verifiability is relativized to each individual, and then there's going to be a version of this that is, uh, just in general. So we say that a sentence is factually significant to any given person if and only if he knows how to verify that proposition which it purports to express. That is, if he knows what observations would lead him, under certain conditions, to accept the proposition as being true or reject it as being false. So this is what makes something, uh, factually significant. That means capable of having truth value. Um, if, on the other hand, the putative proposition is of such a character that the assumption of its truth or falsehood is consistent with any assumptions whatsoever concerning the nature of his future experience, that is, nothing could count as evidence for or against it in his future experiences. So, for example, um, an example of something that fails this test is, "We could live in The Matrix." We're in The Matrix, or as Descartes, if you're familiar with Descartes, Descartes said, "We could be being deceived by a demon deceiver." Our senses, which we think are telling us about the world, could actually be the product of someone just manipulating us, and there is no world, uh, as we think we see it. That claim is one of these claims that fails this criterion because there is no evidence that could disprove it. That's one of the challenges to it. So that makes it, according to Ayer, essentially meaningless. He, as he goes on, "If, on the other hand, the putative proposition is such a character that the assumption of its truth or falsehood is consistent with any assumption whatever concerning the nature of his future experience, then, as far as he is concerned, it is, if not a tautology" – so that's the other alternative, it could be one of these things that's just true by nature of the meanings of the, uh, the words that make it up, true by definition – "if not a tautology, then it is a mere pseudo-proposition."

Okay, what's a pseudo-proposition? So one of the critical objections to, uh, logical positivism, specifically focusing on the verification principle, is it seems to, uh, it seems to lump things together that we would say there's a clear distinction with them. So, for example, "We're in The Matrix" appears to be meaningful. We get what that means. It had the, the, it has words that they appear to be saying something. You know, I understand it. Contrast that with, you know, uh, like, um, in the article by Ziff, where he talks about a grouchy academic responding to a question when he's being tested for sanity, and he just makes noises like "blurle urgle" or whatever. Now, that's meaningless. Whereas we would normally say this is meaningful. So are you saying that we're just lumping them together? Because if you are, that seems to be ignoring an important distinction. That seems to be a count against logical positivism if it says that two things that appear to be clearly distinct are in fact the same. So how can you say that that is a pseudo-proposition? It's not an actual proposition that is asserting some claim. Well, this is where, um, the positivists really love Russell's theory of descriptions. Not so much, it, in what it does for what it literally does, applying to definite descriptions, but in what it's an example of. What it's an example of is taking the surface grammar of, uh, a statement in natural language, in this case, English, and showing that the logical grammar is different from the surface grammar. So in Russell's theory of descriptions, he says, uh, the way we talk in English is we can make something like "the King of France," which is a definite description. We can make that the subject of a sentence. And if we're committed to this idea that the meaning of, um, of a sentence is in part to do with, uh, what it picks out about the world, and if we think that the meaning of singular terms like names or like apparently definite descriptions is simply the objects they pick out in the world, then there's a problem with statements like "The King of France is bald" because there is no King of France. Now, Meinong solved this problem by saying, "Okay, well, there must be, in some sense, a King of France." So he solved, he was so committed to the idea that the meaning of a term, a singular term, was the thing that it picked out, was that he said there must be, there must always be a thing that they picked out, even when there isn't such a thing in the real world. So he, he postulated this sort of spirit world where all of the possible things that we could talk about existed. So the King of France, in some sense, had this kind of shadow existence. Russell, uh, and Quine in particular, were scathing about this and said, you know, it's like an ontological slum. You're just peopling the universe with, with stuff that shouldn't be there. And Russell has this, uh, clever a solution where he, uh, explains that the surface grammar, the English sentence where the, uh, the King of France plays the same role as a name would, is misleading. And really, the underlying grammar, the actual what the sentence is actually saying, which can be revealed by predicate logic, is something very different. It, in fact, you replace a term with a quantifier and a variable. So this little trick is seen as like, "Wow, that's what philosophy can do." That's the ideal of what philosophy can do. Philosophy can, and this is something Wittgenstein, um, uh, said in his early work, and actually was committed to in his later work too, is that the job of philosophy is to clear up misconceptions. Because actually, the important stuff about finding out important truths about the world, these guys concede to science. Science does that. Science has the methodology for that. What we're doing is just the best thing we can come up with is, uh, Tories is analytic truths. Uh, what philosophy can do that is valuable still is we can show how sentences that appear meaningful in, uh, English, like "We're in The Matrix," as contrasted with "blurle ugle," actually fail to say anything. So just as the theory of descriptions exposes that there's a difference between what is really being said by an apparently meaningful sentence, uh, is, uh, so philosophy can do that for just about any of the sentences of metaphysics.

So, Ayer himself quotes, rather cheekily, a sentence from Bradley: "The Absolute enters into, but is itself incapable of, evolution and progress." Now, this, uh, is obviously a meaningful English sentence. We would normally say. But what he's going to say is, "No, it's a grammatical sentence, but probably he would say it's like sentences that classic example of a sentence that has syntax but not semantics, is syntactically correct but has no semantic meaning, which is 'Colorless green ideas sleep furiously.'" So he would say that's basically what this is. Sure, it looks like it should be meaningful because it's got words in the right order and adjectives where there should be adjectives and so on. But when you look at it, and when you apply the principle, then, um, you, you find that actually it does nothing. So a helpful slogan, uh, for logical positivism is, "A difference must make a difference." That is, if there's a difference in meaning between two statements, this must register as a difference that we could verify. That, that it would, there would be something that we could experience that would reveal the difference. So yes, the logical positivists are very much influenced by empiricists like Hume. That is, knowledge comes from our senses, so there has to be sensory, um, input in the future that would reveal the difference, which is why "We're in The Matrix" is meaningless because, uh, that essentially is a claim that all of our senses are misleading, and that so none of our senses could reveal that our senses are misleading.

Now, there's a worry, uh, about the formulation of the verification principle. You can, and this is revealed, this is talked about in the, uh, well, actually Ayer himself talks about this. He makes two distinctions between types of verifiability. So, uh, there's "practical verifiability" versus "verifiability in principle." Now, think of a claim: "There are mountains on the far side of the moon." Does that pass the verification test? Well, not if we are still focusing on, is it meaningful for me? Then no, it appears not to, because there is no experience. I'm never going to be on the far side of the moon. I'm never going to see. I'm maybe I'm a quitter in saying that, but I'm pretty certain that I'm never going to see the far side of the moon. So I cannot verify that. Does that mean that this is, is a meaningless statement? Well, it would be very dangerous for the logical positivist project if that were true, because then that would seem to rule out huge chunks of science. And the verificationist, I'm sorry, the positivists absolutely don't want to step on science's toes. They think legitimate science is, you know, the greatest product of human ingenuity in history, then, and that they should be a service to. So if they start saying that big chunks of science, uh, are meaningless, then something's gone wrong. So, uh, he says, "Okay, obviously practical is too strong. We should talk about verifiability in principle." So "in principle" means, even though we can't actually, uh, verify whether or not there are mountains on the, uh, far side of the moon, we know what it would take to do so. We can specify the conditions that would be necessary, necessary to do so. Whereas "The Absolute enters into, but is itself incapable of, evolution and progress," there we can't even specify it. So this passes, this fails. That's what we want, uh, because we've, we've weakened it from practical to in principle.

Similarly, there's "strong" versus "weak." Strong is the truth of the statement can be, uh, conclusively established. That is too strong, because there are certainly things. I mean, it seems like, uh, Hume, another thing that Hume pointed out is that statements like the generalization of science, like for example, "Water boils at 100 degrees Centigrade." That's a generalization because it's about all water at any time in any place. It's not talking about this particular chunk of this particular sample of water. It's saying, this is true of all water. So that's a generalization. Could we prove that to be true? Well, one of the things Hume's famously pointed out is that no, we can't. Because in order to prove that to be true, we would have to prove that all water behaves the same. But we can't do that. Because we can't test all water. We can't test the water in the future. We can't test, uh, water beyond, uh, the light cone in our universe. Um, so we cannot prove something that would need to be proved for us to, uh, prove any generalization in science. So, uh, instead, we need "weak" verifiability. That is, weak doesn't prove it conclusively, but, uh, it is weakly verifiable if it is possible for experience to render it probable. So, uh, depending on your account of probability, the more that you test water and in various circumstances, well, no, it would have to be at, uh, it would have to be at, um, sea level, wouldn't it? Because, you know, water boils at different temperatures at different pressures. Well, whatever, in a particular, in, you know, sea level at particular pressure, the more we test water in those conditions and it boils at 100 degrees Centigrade, the more we appear to have confirmed, uh, inductively, those generalizations.

Now, there's a problem with this. Actually, this is where Popper was most critical of the positivists. He says that you can't actually inductively confirm anything. So Popper famously comes up with an alternative criterion for testing in science, which is falsifiability, and we'll come to that, uh, in another video. However, that's the basic idea. And it seems like a good idea. It does seem like, uh, an awful lot of philosophy, particularly if you're an analytic philosopher, an awful lot of Continental philosophy, of which Heidegger is basically the most, uh, lauded practitioner, an awful lot of Continental philosophy seems suspiciously like it seems like it's just making words without meaning. So even though logical positivism is considered in the past, like I said, analytic philosophy is committed to the same idea that you should at least your words should mean something, and that's the core idea here. The core idea is, and there has to be a test for meaningfulness. So yes, actually, let's draw a distinction between the "criterion of meaningfulness," which is what Ayer is defending, and what Schlick seems to be suggesting, which is "the meaning of a proposition is its method of verification." Notice the difference. Um, Ayer isn't saying that the meaning is the verification, he's saying in order for it to be meaningful, it has to pass this test. So criterion is a test for whether or not it has meaning, whereas an account of meaning says, "Here's what the meaning is. This is what meaning consists in." Now, that seems more extreme than this, because it just doesn't seem like it just doesn't seem right to say that the meaning of something is its method of verification. Uh, a criticism of this was, suppose you came up with a machine that was an infallible, or you know, discovered this alien computer that was an infallible test of whether or not, uh, something could be verified. Then it looks like the meaning of every sentence would be, um, the result of that computer, and that isn't what the meaning of sentences are. Sentences are about things in the world, they're not about the computer itself. So that seems like a bit of a non-starter. But this looks better. Um, but notice how much it rules out. For example, Ayer in *Language, Truth and Logic* says he's not an atheist. Does he believe in God? No. Uh, then why isn't he an atheist? He isn't an atheist because he says an atheist is someone for whom the statement "God exists" has truth value. It's false, obviously, if you're an atheist, you think "God exists" is false. Whereas he, Ayer, didn't think that it was true or false. He thought that the statement "God exists" is meaningless, why? Because it fails the verification principle. There is no evidence that would count for or against it.

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Um, so in a sense, he's even more extreme than an atheist, because an atheist will at least debate the issue, whereas, uh, Ayer would say, "Just all God talk is meaningless." What else? Ethics. Now, uh, that's wrong. What kind of evidence would count in support of the claim that's wrong? Well, another famous quote from Hume is, "You cannot derive an 'ought' (which is a moral or normative statement) from an 'is' (which is a factual statement)." So, in other words, there's the world that science describes, there's ethics, and the world doesn't tell us anything about ethics. Well, uh-oh, then it means that nothing will verify ethical statements like "killing is wrong." So does that mean ethics is meaningless? Well, actually, what Hume, what Ayer says in *Language, Truth and Logic* is he commits himself to, uh, a theory called emotivism. And emotivism is sometimes referred to as the "Boo-Hoorah" view of ethics in the British version, or the American version is the "Yuck-Yay" theory, which is that actually ethical statements do have meaning, but the meaning isn't what most people think. The meaning of ethical statements is just about the emotional response of the person who said them. So, in other words, what "killing is wrong" means when I say it is, killing evokes in me a feeling of disgust or, you know, moral outrage. Some, but that's an emotion. It's not outrage about some moral issue, because moral, there's, there's no such thing as morality above and beyond humans' visceral reactions to things. So, in other words, when I say, um, "killing is wrong," it's as if I'm saying "killing, boo!" or "killing, yuck!" Um, whereas if I approve of something, I'm saying, you know, if I say, "charity is good," then it's like "charity, yay!" Um, and so, uh, Ayer says, "Well, look, I'm not saying that they're meaningless, but I'm just saying that they don't mean there are no logical facts out there in the world. There's just what people feel about things." Now, this theory of ethics has been pretty much, uh, decisively trashed, almost immediately after it was proposed. There's a guy called Stevenson who probably gave the best formulation of it, but it's pretty much rejected. And that's the trouble with, with, uh, that's the reason logical positivism is dead, is it commits itself to a lot of other theses that, uh, have been trashed.

So, for example, think of psychology. If, uh, if psychology is talking about the mental states of other people, what kind of evidence do we have that those other people have mental states? This is the problem of other minds. We cannot access their mental states. There's no such thing as telepathy. I cannot get inside your head. So if psychology is to be a, a, uh, factual, if there are to be factual statements of psychology, they cannot be directly about what's going on in your head, because that's not verifiable to me. So the only kind of things that are verifiable that we think are related to, uh, mental states are behaviors. So, for example, the statement, "So-and-so is in pain." What that actually, what the verifiable conditions of it are, is pain behavior. So, "so-and-so is in pain" means they winced and did this. And of course, there are all kinds of problems with, uh, this kind of behaviorism. This isn't behaviorism in the sense of B.F. Skinner, um, but it's, it's kind of a logical behaviorism. It's that the only kind of evidence that would count about other people's mental states is their observable behavior. And of course, there's all kinds of, the most obvious problem with behavior is people can act, or somebody stoic could be in pain and hide it, and somebody who's a faker could not be in pain and exhibit the behavior. So it just doesn't seem correct. Now, what the positivists would say is, "That's the best we got to go on." You know, if you're going to claim that people are in pain because you know that they're in pain because you have access to their minds, that's, you don't. So if you're going to make claims that are actually legitimately meaningful, they have to be behaviorist claims.

There's, uh, other problems. For example, what kind of evidence counts about the existence of electrons? Well, we can't directly observe electrons. That the ideal, the ideal of the Vienna Circle is that the way science works is the core claims of science tend to be very theoretical and isolated, but from observation. But we want to say that they're meaningful and that they tell us something about the world. So there has to be a way to connect those core claims, like generalizations, like Newton's laws or something like that. There has to be a way to connect those to actual observable experience, because otherwise it fails the verifiable, uh, the verifiability criterion. So, this is where logic comes in. Logic connects, uh, general principles that seem to be very far removed from observational claims, connects them to actual observational claims. So, general claims plus logic implies that this would be true, and we observe that being true. And so this is why, actually, you need a priori truths, because we need logic to connect general claims in science to observation sentences. So there's this idea that there are sentences that are directly confirmable by direct experience. That again is another contentious issue. What counts as an observation sentence? Is it, is an observation sentence something like, "I see, I see a cow," or something like that? Or does an observation sentence have to be even more basic, like "I see pattern," "I have, I have certain patterns of sensory stimulation"? Because actually, what, uh, Descartes pointed out is that you don't know you see a cow, you just think you're seeing a cow because you're having a cow experience, but it could be a demon deceiver. So depending on the positivist, it's, observation sentences are actually just about our experiences, or if they're more bold, then you can say, "No, you're, you're legitimately experiencing the external world." So that's the sort of picture that science is great because it's tied to reality. There are observation sentences that confirm, that have an influence on, uh, whether or not the claims of science are true or false. So therefore, they're verifiable, they pass the test. Whereas stuff like what Bradley and Heidegger are saying fail the test and can be consigned to the flames. What people like Popper and Quine and other critics point out is it's just not that simple. And this, this kind of rosy picture of observation sentences being possible, uh, doesn't hold up the more you look at it. And Carnap basically spent the rest of his life qualifying and trying to work on this model and come up with a, a workable model.

Let's look at some objections. It only applies to part of language. That is, we've seen when we were talking about, um, when we were talking about Grice's theory of meaning and the ordinary language philosophers, they pointed out that all kinds of sentences were meaningful that didn't, that you couldn't, you couldn't process in the way that Frege and Russell do. That is, questions, commands, things like that. These are meaningful, even though they don't tell you something that is either true or false. How, how do you verify a question? You don't. So does that mean that it's not meaningful? That questions aren't meaningful? It seems like this criterion misses out a huge chunk of meaningful language. Now, as Miller points out, uh, uh, Ayer himself, when he introduces the, um, the criterion of verifiability, he does go on to suggest how it can cover things like questions. He goes on and he says, "And with regard to questions, the procedure is the same. We acquire in every case what observations would lead us to the answer the question one way or the other. And if none can be discovered, we must conclude that the sentence under consideration does not express a genuine question." So, uh, what kind of circumstances would cause us to answer the question, "Does that work?" Well, if it does work, then you can respond to this kind of criticism. We've already looked at this problem. It looks like, uh, logical positivism seems to lump together things we want to say are meaningful, like "We're in The Matrix," with like literally meaningless sounds. Um, but what the logical positivist can say in response is, "This just has the appearance of meaning, but actually it's like 'Colorless green ideas sleep furiously.'" We've talked about this. It leads to behaviorism, and people just don't think the meaning of "he's in pain" is "he's wincing." They think it's talking about actual experiences. Here's a key, uh, problem. It seems like the principle itself, the verification principle, fails its own test. It has to be either a priori or it has to be testable. Well, it's not a priori. It doesn't seem to be true by definition. Uh, is it testable? What kind of evidence would count in support of the verification principle? That is, that sentences are meaningless unless they're, um, unless they can be verified. It doesn't look like it can. So it looks like, uh, it's kind of hypocritical of the verificationist to present this criterion. What counts as direct observation? We've talked about that. Is it like experience, uh, that individuals have? And of course, then my, um, observation is completely irrelevant to you, because my observation is sensations that I have that you can't access. Uh, another problem is, if math is analytic, as the early Wittgenstein says, and, and the positivists say, well, that means all of the truths of math are just true by definition. So they're true on the basis of how we've defined the terms. Well, in that case, why is math useful? Why, if we invented it, and just math is just a product of our definitions, why does math explain so much about the world? And, uh, why are mathematicians awarded prizes for discoveries? Um, um, well, Ayer has got a response to that. He says, actually, of philosophy, which is also an a priori, uh, an analytic activity, of philosophy and math, he says it's basically just, uh, if we were God-like, if we were omniscient, um, we would, uh, understand all the truths of math and philosophy at once, and there would be no discoveries. So discoveries are just a byproduct of us being limited beings. It's like, uh, we're finally getting to something that was obvious to the omnipotent being from just the meaning of the words. It's just that we can't keep it all in our head at once, but it's all there at once, it's all consistent. Um, that's his response. Whether or not that's, um, convincing, that's for the philosophers of math to, um, debate.

So long story short, what the logical positivists contribute to, the main focus was science and philosophy of science, but also this principle, uh, claim about language is that language is only, bits of language are only meaningful in so far as they can be tested or they can be verified. Uh, so they connect meaning to verifiability. And this seems like it would be wonderful if it was true, because it would be, it would provide us with a way of just trashing the, you know, and when somebody, uh, tells you something that you know seems to be meaningless, you say, "Look, what kind of evidence would confirm or deny what you're saying?" It does seem like there's an important core idea here, but it turns out when you work out all the details, it just doesn't seem to hold water. But as I said, they have had a lasting effect on, uh, they've had good and bad effects on, on analytic philosophy. Good in the sense that clarity is important, and there's less than there was, uh, at least in analytic philosophy. Bad in that they, uh, set back the study of fields like ethics and fields like political science and political philosophy and metaphysics, because they said that's all, you don't have to do that, forget all that stuff. So consequently, you know, doing that kind of philosophy was for a time very much discredited. It was like you were doing alchemy or something, because you were doing something that had been shown to be pointless. And, uh, it was only sort of by the 70s that these fields started to explode again, um, once the influence of the positivists had finally waned. Logical positivism.