- Who are some others? (you're probably the best-versed in this area, Larry) --Seb
- I might not be. Anyway, all the logical empiricists talked about it (i.e., discussed it, as an alternative to the verifiability theory of meaning), and it's an essential concept in the philosophy of science. It wasn't owned by Popper. Hopefully I'll get a chance to write up what I know about the topic soon, but probably somebody'll beat me to it. :-) --LMS
I think all Conspiracy theories are unfalsifiable. They can be proven true, but they can't be procen false. From the article about Conspiracy Theories: A conspiracy theory is the exact opposite of a [scientific theory]?, in that it cannot be refuted: even evidence to the contrary is taken by the conspiracy theorist to support the notion that an extremely powerful conspiracy is at work, that just has fabricated this evidence.
Conspiracy theorists usually reject only some kinds of evidence, those they think could have been falsified by members of the conspiracy. But there's still many kinds of evidence that they accept, most notably "scientific" evidence. --Taw
"All green things are green" is not a good argument, given that philosophy of language people have "grue" and "bleen". A scientist observing a "grue" item would agree that it is green, until it transforms. GregLindahl [ The article now talks a bunch about Quine, who is the philosopher of language in question. ]
- You could always read a book about the history of science, and then write the definition yourself. GregLindahl
- Hey, hey, hey - let's play nice. (IMHO) there's nothing wrong with saying "I think there should be more info on Wikipedia on 'X', but I'm not qualified to do it. Anybody?"
- A couple excerpts from Webster's New Universal Unabridged Dictionary:
- falsifiable: capable of being falsified.
- falsify: 2. to show to be unfounded or untrue; to disprove; to prove to be false.
- There are other definitions of falsify, but I'm confident the above is the relevant one. It would seem that the question is whether there could exist any evidence which, if presented, would clearly demonstrate that the proposition in question is false.
Thanks, Wesley. Now how do work that definition into the body of the article? It's pertinent to reams of talk about Creationism and Evolution. Ed Poor
- It ain't the definition that's the problem, it's the nitty-gritty. If I say that (for example) I've falsified the hypothesis that Argon dating is accurate, and you don't agree, how do we come to a consensus?
Um, you don't get it. Everyone would agree that "Argon dating is accurate" is a falsifiable statement. GregLindahl
Moved here to /Talk until we decide whether this is or isn't an example of falsifiability.
"For example, before the 1960s, there was no way to disprove the proposition that there were little green men living on the other side of the moon. So it wasn't considered a scientific hypothesis. When it became possible to examine the moon closely with spacecraft-mounted cameras, the proposition gained falsifiability, because there was a way to disprove it. Alas, the "moon men" hypothesis's viability lasted only a short time, as an exhaustive photographic survey of the moon showed no evidence of life on the moon."
The Little Green Man example is poor; we knew in the 1960s that eventually we would be able to prove whether or not LGMs lived on the back side of the Moon. Unfalsifiability is generally reserved for things which are considered to NEVER be falsifiable. Again, reading a book about the philosophy and history of science is probably a better way of learning about this topic... much better than giving incorrect examples all over Wikipedia. GregLindahl
- You're begging for it, and here it comes. Go up one level in a minute or two.
Re your "Moon man" example: No, I think that's wrong. The idea is that if something is in principle unfalsifiable, then it isn't Science. I.e., "Are there little green men on the moon?" "Go check." "But it's far." "Well, build a rocket or something." -- in theory we can imagine a check or test of our hypothesis.
But something like "God created the Universe ten minutes ago exactly as we see it, including our memories" is an "airtight" hypothesis, no way to disprove, and not Science, by definition.
- Thank you, that's a classic example of falsifiability, one that Ed would run into if he educated himself by, say, reading a book, as opposed to posting wrong stuff on Wikipedia. GregLindahl
The theory of evolution as generally taught. It is not falsifiable, because it claims that God has nothing to do with the appearance of new species of life. There is no way to falsify this claim (as it is dependent upon an unfalsifiable premise), so it's not a scientific hypothesis, only a philosophical conjecture. People who claim to be scientists can make unscientific (and unfalsifiable) claims.
I disagree. The theory of evolution does not claim that God has nothing to do with the appearance of new species of life. It's quite possible that God saw evolution as a nice quick way of creating a stable ecosystem from basic components without creating each in turn. After all - it's the original genetic algorithm! And nothing stops God from carefully fiddling about with a pile of carbon atoms in deepest darkest Africa and creating something new.
So lets jettison the 'God' argument, and reduce this to the statement "Darwin's Theory of Evolution is non-falsifiable". At the present moment in time, there is no way in which we can go back in time and watch evolution take place. So at the moment it is unfalsifiable. However, in a billion years time (when we'll all be getting worried about the sun going red giant on us) there will be 1000 million years of data to look back on. If no new species arise, then patently it is false; if radically different species (ie: unrelated species) arise, then patently it is false; if we see evolution occurring then it appears to be true. At this point, it can be falsified.
It should be pointed out that the theory of evolution has a major caveat in it's title: it is a theory, not a proof. Theories are by definition unproven, and for all science (excepting the man-made sciences such as Mathematics) nothing can be conclusively proven. The best that can be hoped for is this: the theory must make a prediction prior to the making of an experiment, and must agree with all future experiments in this field. Darwin's theory of evolution does this (just) - therefore it is falsifiable. Given (lots of) time.
However, there are no other theories (by the definition of making a prediction) about how the species evolve (or, at least, I haven't heard of them). So the theory of evolution is the best working theory so far.
(Also, it might be a good example to put a good example of a scientific theory being found false, and how it could have been considered falsifiable before the evidence to the contrary: Newton's laws of motion might be a good choice.)
Please let me know at my name page if you add to this conversation.
Natural selection can also be falsified without the wait, as even though speciation takes a long time, you can still witness the various stages of the process in different species. Plus the theory makes some predictions about the fossil record that one could go back and check, though I suppose these are more for checking gradual evolution than any particular mechanism. A historically important alternative to Darwin was Lamarck, which claimed that organisms aquire new traits through practice and then pass these on to their offspring. A step in the right direction, proved incorrect.
- "it might be a good example to put a good example of a scientific theory being found false, and how it could have been considered falsifiable before the evidence to the contrary: Newton's laws of motion might be a good choice."
- As I understand this, Newton's laws of motion have not been found false, but are rather a "special case" under Relativity (which admittedly seems to apply to 99% of situations humans encounter).
- Thanks for the input! Dave McKee
I restored the point about a theory as taught, (with an added explanation) since it was bringing in a different aspect of unfalsifiability not mentioned in the other points listed. I also added two more points, (one from /talk) about what is involved in unfalsifiabilty.
I removed this because it is either false or redundant:
- The theory of evolution as generally taught: It is not falsifiable, because it claims that God has nothing to do with the appearance of new species of life. There is no way to falsify this claim (as it is dependent upon an unfalsifiable premise), so it's not a scientific hypothesis, only a philosophical conjecture. People who claim to be scientists can make unscientific (and unfalsifiable) claims. Note that its unfalsifiability is not due to the subject material being taught, but by the method that is being used in the teaching.
If by "as taught", you mean that most teachers of evolution explicitly teach the non-existence of God, this is false. And even if it were true, the first example here already points out that both the existence and non-existence of God are nonfalsifiable, so it is redundant. --LDC
I'm glad you have lived in a world where teachers of evolution do not teach the non-existence of God. I, however, would like to see evidence other than your simple statement that this world really exists. My experience certainly differs from yours, and feel the item should be included in this article. -- BenBaker
I am placing this item back into Falsifiability. It is pointing out that unfalisfiability is transitive, and brings up the proper point that just because something is taught doesn't mean that it is falsifiable. I would be happy to edit it to include a different example if Lee provides one, but this example, in my experience, is one that has maximual impact on the reader, and thus is appropriate for an encyclopedia.
It seems to me that the inclusion in Falsifiability of an example about evolution being unfalsifiable is in irreconcible conflict with the (scientific) criticism of Intelligent Design, Creationism, or whatever we're going to wind up calling it.
I'd like to see wiser heads than mine come up with a definition that enables the intelligent layman to discern whether a given hypothesis is falsifiable and thus entitiled to status as a "scientific" hypothesis.
- Yes, it was a conflict, because it was nonsense. I put it where it belongs. I also added a clearer definition, and clarified the examples. It should now be understandable to anyone. --LDC
- Excellent work! We now have an encyclopedia article on falsifiability, and my little green men can go back to Pluto for a well-earned rest :-) --Ed Poor
Ben, I undid some of your changes: they're certainly not wrong, and I see why you might want to include them for rigor, but I don't think this particular article is the place for that. This is a high-level overview of what is really a very simple concept, and I think it's important to keep the examples simple and straightforward. I also think it's reasonable to group the falisifiable one into things like "physics" and "evolution"; otherwise there will be hundreds of them. --LDC
I also removed:
- Reciprocal System of Theory: A theory that, its present form, does not contain any mathematical properties and therefore does not make exact numerical predictions, making it impossible to compare and test against the established scientific theories.
While it certainly qualifies, it's not important enough to even merit being a bad example. Let's keep this explanation simple and the examples common, everyday things that people can relate to. --LDC
- Yes, by golly! Your explanation is so clear that I, a mere layman, can grasp it. Thanks indeed. --Ed Poor
I don't know a better article for it, and think it is specious to create one just because you don't like to see them. I certainly don't agree the two explanations should be summarily deleted. I think if one looks in an encyclopedia for an article on a simple subject, the writers have an obligation to treat all aspects carefully and not avoid to bring up views or ideas because they are complex. (although I don't consider either of these to be complex, and am confused by who Ed Poor is agreeing with, unless he is using subtle sarcasm.)
- No, being subtle is not my style, I really am a mere layman. I really did find LDC's example clear enough to use -- for everyday purposes, at least. The new rewrite is even better. At last I will be able to determine whether the theory of evolution or Intelligent Design are falsifiable, and all will agree :-) --Ed Poor
As I said before, each of these were placed in the article for particular purposes. You agreed the purposes are appropriate (I think), but you deleted them anyway. I agreed I would not re-edit if you should have better examples that fulfilled the purposes discussed. You did not. You simply deleted them. To my knowledge, this means I am required by intellectual honesty and forthrightness to replace them in the article. Please show me that I am wrong if you disagree. -- BenBaker
I'm not sure what you're arguing about here: the changes I made were mostly to simplify the prose of sections that remain here (you put in some parentheticals that weren't relaly necessary, and that obscure the main point). That's mainly an issue of writing style. The only things I removed were not things I thought you put in. They were (1) The reciprocal system, for the reason I note above (no one has heard of it, it doesn't deserve to be even a bad example, and it provides no information on the subject that isn't already here); and (2) the "evolution as generally taught" example, because it is clearly false. If you think either of those does belong here, please explain why. --LDC
I'm always fighting for the underdog's right to be heard, as long as they state it clearly. Hence my support for paragraphs I didn't write. That said, I have explained why I think those two items should be included. I will try again, but briefly, as I think you can scroll back and re-read my previous points.
1) Teaching science as dogma is not good. Falsifiability is essential to a proper understanding of the scientific method. Even if the theory is one that someone may have evidence to support, (such as the Theory of Evolution).
- I totally agree. If you want to add an example for "theories of evolution that deny the role of God", it would be true (as oppose to "as generally taught", which is false because evolution as generally taught makes no mention of God at all). But even then, it would just be a repeat of the first example. I'm sure there's a better example of something frequently taught in a mistaken way, or frequently espoused by scientists--I'll look for one.
2) non-Falsifiability is transitive. A theory dependent upon a non-falsifiable theory is also non-falsifiable.
- That's true. If you have a good example of this, make it a separate paragraph and expalain that. Maybe at the end after the examples.
3) Falsifiablity requires a clear, unambiguous formulation, such as that provided by mathematics. The Reciprocal System of Theory (which I had not heard of prior to today) is an example of such a formulation.
- I just disagree here. It's really a simple idea, and we should emphasize that it is a simple idea, although rigorously applying it may sometimes be difficult. If you have a better example (i.e., someting that peole have actually heard of and care about) that makes the point you're aiming at, it might be worth including.
4) The teaching science example is NOT false, in my experience.
- I, for one, have never seen an American middle-school biology text that mentioned God in any way, and given the fact that school boards are infested with Christians all over the country who are quick to pounce on anything anti-Christian, any publisher who actually put text denying the existance of God or denying the role of God in human creation wouldn't sell a single copy, and would probably be lynched. It just isn't done, and I cannot imagine how you can think it is. -- LDC
- I agree with you on your assessment. I don't agree that what is written is the same as what is taught. I tend to be very understanding of other people's beliefs. That doesn't mean that I am naive enough to think that they don't have them. I have heard too many 'side comments' to say that non-God evolutionary theory is not being actively taught in the U.S. school system, from elementary schools through graduate schools.
On a different note, should the different sub-theories of the Theory of Evolution be lumped into one paragraph ? I think they are distinct, and should be able to stand on their own as falsifiable or non-falsifiable. I appreciate the wikifying to RNA and proteins, btw. I simply argue that it is actions like these that promote the idea that there is a single monolithic Theory of Evolution, rather than a dynamic constellation of theories all elaborating different aspects of the subject. -- BenBaker
- Yes, they are separate ideas; the grouping is a matter of style, because otherwise the list of falsifiable ideas I fear will become long and unwieldy. Grouping is a good technique for simplifying prose.
- Also, I have to say that even if some particular sentence, example, or explanation is completely true and relevant, that doesn't necessarily mean that the article is better with it than without it. One has to look at a piece of prose as a whole, and decide if it makes the point clearly or if the extra weight of explanation actually gets in the way. We're not writing for scientists here, we're writing for laymen.
--- I await your (LDC or other's) work on finding alternate examples. I do think that some examples should be provided. I don't agree that if you don't like the examples, that the points should not be made. My understanding of intellectually honesty requires that I provide information about a topic that I know is relevant to it. -- BenBaker Btw, I'm glad Ed thinks the article is shaping up.
There are some paragraphs now that try to address my concerns with this article. I'm glad of that. The Ten-minute-ago universe has been deleted. I don't know why. The supernatural creation of the universe is still there, but I don't think the Omphalos theory is the same as the ten-minute-ago, since it can easily be misinterpreted as the supernatural nature is what is unfalsifiable, not the sudden creation that is unfalsifiable.
- I moved the detailed description of Omphalos (and its cousin, the ten-minute creation) to their own article. Those details aren't relevant here, but I didn't want to delete them entirely.
On the issue of things that are falsifiable, I'd like to hear the input of others would consider the following situation to show the existence of God as falsifiable.
Since God is omnipotent, if God wanted to make his existence incontrovertible, he could simply answer any question of his existence whenever it occurs. Every experiment that could show he didn't exist would fail and every one that could show he does exist would succeed. Note that this is not based the bare facts of the experiment, but would need to be "reading the heart or intent" of the experimentor. Now in my opinion, a world in which God did this would be drastically different from the world we live in. Free Will would mean the choice to follow God, rather than to believe whether God exists. Now if that world did exist, would the existence of God be falsifiable or would it just be proved?
- Hmm. I'll have to think about what you mean here, and how it relates to this article. I think it might be more relevant to ontology/metaphysics than epistemology, though. --LDC
Can the article distinguish between things that "can't be tested now" because we (1) don't know how or (2) think we never will be able to, as opposed to (3) matters which are logically or philosophically impossible to test?
I want to know this, because it has a direct bearing on the Creationism debate. ID's status as scientific or unscientific depends mainly on falsifiability, so a clear definition will help me. Um, can I motivate you by promising not to "vandalize" the evolution and creationism pages (wink)? --Ed Poor
That sounds like a distinction worth making. I'll think about how to do that. --LDC
- That was quick thinking, it's already there. Thanks. --Ed Poor
- Modern theories of evolution. The theory as a whole could be falsified by finding an anomalous fossil of an advanced life form in rocks dated before that life form or its ancestors could have evolved (for example, finding a mammal in pre-Cambrian sediment). The theory of common descent could be falsified by finding a unique form of Earthly life that was totally unrelated to any existing or fossil form (for example, one not using RNA or proteins). The theory of sexual selection could be falsified by finding an organism with colorful sexual selection markings that was blind.
I removed this from the article, because what we really need, I suppose, is a discussion of the various views about the falsifiability of the theory of evolution and of creationism. Giving one as an example of an unfalsifiable theory and the otehr as an example of a falsifiable theory just won't do: it really is NPOV.
- Any theory based upon a non-falsifiable premise is itself non-falsifiable. For example, a physical theory that posits multiple parallel universes with which we cannot interact is necessarily non-flasifiable. If the premise is changed to allow some theoretical mechanism by which we can see or change something in those universes, then it might theoretically become testable.
I removed this too; I don't see what the point of it is, and it sounds quite possible controversial to me (sounds like a topic a philosopher of science might write some dry journal article about).
- It should be noted that while the criterion of falsifiability is a foundation of modern science, many scientists and educators are lax in its application to their beliefs in general. For example, many scientists hold and express strong opinions about the existence of God or the non-existence of God, even though such beliefs are not falsifiable and thus not scientific.
I removed this. It is totally controversial whether the existence of God is not falsifiable.
- Likewise, scientists may often speculate or extend analogies to offer explanations for things that are not yet easily testable, and thus not falsifiable.
Yeah, but so what? Why are we saying this in an article about falsifiability? If you want to describe the controversy between evolutionary theory and creationism, do so explicitly. Don't use this article as a platform to state platitudes that are supposed to persuade people of your views.
- For example, some theories like evolutionary psychology are offered as explanations for human behavior even though we presently lack the technology to rigorously test what causes human behavior. These theories are only falsifiable and "scientific" to the degree that they predict some future means of being able to test them, or that individual facts predicted by the theory might be testable on their own.
The above strikes me as original research, not as a statement of what is generally known and believed about evolutionary psychology. I.e., not neutral point of view.
- There are also degrees of falsifiability, and scientific hypotheses are considered superior if they are more falsifiable than competing ones.
I've never heard of such a thing as "degrees of falsifiability."
- For example, a hypothesis for which there are many presently available tests (such as most physical laws) is superior to one that may only be testable in the future with some new technology (such as some psychological theories), and those are in turn superior to hypotheses that can never be tested because they are fundamentally untestable by their very nature (such as the existence or non-existence of God).
And here we've got a lot of talk about what hypotheses are superior to others because they're falsifiable. I would like to have a source for this stuff. --LMS
Somebody could do this article (as well as scientific method) a great service by finding an actual philosopher of science to spruce it up. The article as it stood was pretty appalling--it still is nowhere near being something I'd want other philosophers to look at, but it least it doesn't contain any obviously bad mistakes, as the earlier version did. --LMS
Great rewrite Larry. This subject probably does deserve a more rigorous treatment from a serious philosopher, and the history is certainly worthwhile. The falsifiability of modern evolutionary theories probably does deserve an article of its own, and there is certainly some contention there even among scientists. The transitivity comment seemed to me to be bloody obvious and not that useful, but it seemed important to someone else, so I was being diplomatic. I agree the article is better without it.
While you may be right that academic philosophers do not use the term "degrees of falsifiability", Popper specifically did, and proposed a related measure he called verisimilitude, even going so far as to offer mathematical inequalities for comparing the verisimiltude of various statements.
- I just didn't know that (which goes to show you how much I know about Popper). Maybe it should be put into the article and attributed to Popper, then.
It is very common for working scientists to rate one hypothesis as "superior" to another on grounds of testability--that's mentioned all the time in journal articles.
- Of course! But do they put it in terms of testability or falsifiability? They're different (though, of course, closely related).
But then working scientists aren't generally philosophers of science. I do think that a philosophy of science actually used by working scientists (whether or not they recognize it as such) is worth mentioning here; if philosophers don't mention it, then they've simply missed it.
I also think some of the examples you removed, while perhaps not commonly used by philosophers (perhaps because they aren't that controversial or interesting), may give a better understanding of the field to a layman. I'd rather annoy a few philosophers with trivialities or redundancies than risk confusing our lay audience in our zeal for philosophical rigor. I realize that "popularizer" is someting of an epithet among both philosophers and scientists, but I wear the label proudly. :-) --LDC
- Actually, the article should be of use to both lay people and to philsophers and scientists. It should begin with a very simple presentation of the issues, and then present each wrinkle of the subject as simply as the wrinkle allows.
Merged earlier more concise version with LMS's rewrite. Most Wikipedia users are not seeking philosophy degrees and would benefit from less-technical treatment.
- I think we ought to do our best to satisfy everyone. This means that we should begin by presenting the material at a simple level, but one of which specialists can approve. By no means should we omit relatively complicated points simply because they are more complicated. If they can be simplified without reducing accuracy, let's do that. Or, if we can present a simplified version of a point first followed by the more complicated but more accurate version, that's also perfectly appropriate, I think. --LMS
-- Larry, I agree with your last sentence, plus:
- I think complicated points should go on separate pages
- Most long texts should be broken into several pages for ease of readability, and for enabling users to easily find text that matches their interest.
Ick. Your merge is much worse than either of the previous versions; it's redundant, disorganized; a mere patching together of two reasonable versions into a mess. I reverted to Larry's version. It is clean, to the point, and well written. My point above is merely an attempt to suggest that maybe Larry's version could be tweaked a bit, not to suggest the earlier version was better--Larry was basically right, the earlier version isn't worth saving in that form. While I agree that what we really want is a serious philosopher of science who can write well, Daniel Dennett and Richard Dawkins don't hang around here much, so we'll have to settle for me and Larry and the rest of the crew. But the article as it is now is quite good, and I don't think major changes should be made to it.
I also don't think it's appropriate for anonymous users to make major changes in articles that have already undergone considerable discussion and revision by regulars (actually, I don't think anonymous edits should be allowed at all, but that's a different story). If you really think the article still needs work, tell us who you are and what you think is wrong, and discuss it here as we've been doing. --LDC
- With all due respect, I disagree with all your points. The pre-LMS version had been hashed out over a few weeks or more, was conscise and informative, and helpful for the layperson. LMS's version is better for people seeking info at a non-introductory level.
- Well, one of the things I liked better about the old version was that it was more concise (shorter). I doubt adding to the new version will help that.
- My suggestion for compromise. Make the old version or something like it the main entry; make Larry's text (probably broken into parts) "additional info" available from the main page. (No, I have to reason to believe that my suggestion will be adopted.)(And I'm getting tired of fighting entropy, so I don't intend to do it myself. Have a good one.)
- Well, there are ways in which I could agree with your suggestion. E.g., in time, I can see articles on Popper's views about falsifiability, on the Vienna Circle treatment of falsifiability, on the philosophical analysis of (theories about the meaning or conditions of) falsifiability, etc. But I would certainly not like to see the meat of this article shunted off into an "additional info" article. --LMS
- "I also don't think it's appropriate for anonymous users to make major changes in articles that have already undergone considerable discussion and revision by regulars" -- I believe I was one of the people who contributed to this entry over the last few weeks, at which time it was being debated by Ed Poor and others. I am anonymous, but I have been at least a semi-regular contributor to Wikipedia for several months. I have nothing to be ashamed of here.
- I agree with that!
- Currently, Wikipedia permits anonymous editing, and I am happy to take advantage of this. I strongly believe that content should be judged on its own merits, independently of a name associated with it or lack thereof.
- I agree as well. But on its own merits, the article that I worked on was pretty lame. --AnonymousCoward <-Don't know if this "signature" was added by the original writer or a later "wit".
Someone tried to mention "lax in application" in the body of the article, but (as I've recently learned) such remarks belong in /Talk.
- Dialogue is easier in Talk. One's radically different views are more likely to get a fair hearing, if he makes his case here.
- Wiki Wars don't help anyone. Changes that look arbitary are often simply deleted.
Just my 2¢. --Ed Poor
I would like to have some information about Ayer and especially have a quote. The language of the sentence citing him seems to be a bit odd, probably the sentence is just to terse.
The paragraph in question: Ayer and many others influenced by the logical empiricists have held that claims about morality (such as "murder is evil" and "John was wrong to steal that money") are also not falsifiable and hence strictly meaningless and not part of scientific inquiry (See also non-cognitivism).
'Strictly meaningless' here probably means : 'not a topic of science'
-- Hannes Hirzel
I replaced it yet again. It is'; what Ayer said, and is a very common topic of even elementary philosophy courses. I'll look for a quote, but in the meantime, don't delete it just because you don't understand it--educate yourself in the topic before you edit an article that many people have spent a considerable amount of time, effort, and education on. I may think of a way to reword it if I can't find a quote, or I may not, because it's really quite clear and accurate exactly as it is. Even better, you might do the research yourself to expand the A. J. Ayer article. --LDC
Here's a quote from Ayer's Language, Truth and Logic (1936): Saying that an act is immoral, he says, is like saying it "in a peculiar tone of horror, or writing it with the addition of some special exclamation marks [which] adds nothing to the literal meaning of the sentence. It merely serves to show that the expression of it is attended by certain feelings in the speaker".
I don't think this should be included in the article itself (it belongs in the article on non-cognitivism), but it might help make the meaning of the sentence here clearer.
I'd say it's simply a matter of interpretation, and indeed a controversial one, to say that Ayer thought moral statements were meaningless. We don't need to say that, anyway. It is not as though they have no function in language, on his view; but they are not fact-stating. So, I guess, the only ground on which we could say that he thought moral statements are meaningless is that only fact-stating claims are, "strictly speaking," meaningful. Perhaps Ayer would want to say that--I don't know--but certainly there are plenty of people who think that reference to other speech acts than the "locutionary act" (the act of stating alleged facts, more or less) is necessary to give a full account of meaning, meaning that meaning and thus meaningfulness involves more than just stating facts. On that view, it would be misleading to say that Ayer thought moral statements are meaningless; though I did add "strictly speaking," this was a confusing oversimplification, it seems. --LMS