P. 248 - 250 of "Conjectures and Refutations" ("Appendix: A presumably false yet formally
highly probable non-empirical statement").

Do we really need to invoke demons to see the logical error in scientific reasoning.

Was there any good reason for choosing the antichrist to show the weakness of verifiability? How does the argument go? I'd like to know.

@Ying provides a hint by saying "presumably false yet formally highly probable non-empirical statement". Perhaps understanding someone as great as Karl Popper is above my pay grade but I feel there's a contradiction there obscured by loose terminology. How can something be presumably false yet highly probable. Either Popper's notion of the weakness of verifiability in science is truly hard to grasp or there's a context in which it makes sense to come so close to contradicting oneself. Which is it? Pray tell.

Isn't the whole body of science predicated on it's ability to distinguish true from false?

Here you go, the text in question:

"In the text of this chapter I have drawn attention to the criterion of progress and of rationality based on the comparison of degrees of testability or degrees of the empirical content or explanatory power of
theories. I did so because these degrees have been little discussed so far.

I always thought that the comparison of these degrees leads to a criterion which is more important and more realistic than the simpler criterion of falsifiability which I proposed at the same time, and which has been widely discussed. But this simpler criterion is also needed. In order to show the need for the falsifiability or testability criterion as a criterion of the empirical character of scientific theories, I will discuss, as an example, a simple, purely existential statement which is formulated in purely empirical terms. I hope this example will also provide a reply to the often repeated criticism that it is perverse to exclude purely existential statements from empirical science and to classify them as metaphysical.

My example consists of the following purely existential theory:

'There exists a finite sequence of Latin elegiac couplets such that, if it is pronounced in an appropriate manner at a certain time and place, this is immediately followed by the appearance of the Devil--that is to say, of a man-like creature with two small horns and one cloven hoof.'

Clearly, this untestable theory is, in principle, verifiable. Though according to my criterion of demarcation it is excluded as non-empirical and nonscientific or, if you like, metaphysical, it is not so excluded by those positivists who consider all well-formed statements and especially all verifiable ones as empirical and scientific.

Some of my positivist friends have indeed assured me that they consider my existential statement about the Devil to be empirical. It is empirical though false, they said. And they indicated that I was mistaking false empirical statements for non-empirical ones.

However, I think that the confusion, if any, is not mine. I too believe that the existential statement is false: but I believe that it is a false metaphysical statement. And why, I ask, should anybody who takes it for empirical think that it is false? Empirically, it is irrefutable. No observation in the world can establish its falsity. There can be no empirical grounds for its falsity.

Moreover, it can be easily shown to be highly probable: like all existential statements, it is in an infinite (or sufficiently large) universe almost logically true, to use an expression of Carnap's. Thus, if we take it to be empirical, we have no reason to reject it, and every reason to accept it and to believe in it-especially upon a subjective theory of probable belief.

Probability theory tells us even more: it can be easily proved not only that empirical evidence can never refute an almost logically true existential statement, but that it can never reduce its probability. (Its probability could be reduced only by some information which is at least 'almost logically false', and therefore not by an observational evidence statement.) So the empirical probability or degree of empirical confirmation (in Carnap's sense) of our statement about the devil-summoning spell must for ever remain equal to unity, whatever the facts may be.

It would of course be easy enough for me to amend my criterion of demarcation so as to include such purely existential statements among the empirical statements. I merely should have to admit not only testable or falsifiable statements among the empirical ones, but also statements which may, in principle, be empirically 'verified'.

But I believe that it is better not to amend my original falsifiability criterion. For our example shows that, if we do not wish to accept my existential statement about the spell that summons the devil, we must deny its empirical character (notwithstanding the fact that it can easily be formalized in any model language sufficient for the expression of even the most primitive scientific assertions). By denying the empirical character of my existential statement, I make it possible to reject it on grounds other than observational evidence. (See chapter 8, section 2, for a discussion of such grounds.)

This shows that it is preferable, as I have been trying to make clear for some considerable time, not to assume uncritically that the terms 'empirical' and 'well-formed' (or 'meaningful') must coincide--and that the situation is hardly improved if we assume, uncritically, that probability or probabilistic 'confirmability' may be used as a criterion of the empirical character of statements or theories. For a non-empirical and presumably false statement may have a high degree of probability, as has been shown here."

" it can be easily shown to be highly probable: like all existential statements, it is in an infinite (or sufficiently large) universe almost logically true,"
Isn't he just speculating on the Multiverse theory that postulates an infinite number of copies of You exists. This can make the logical conclusion that a probable copy of You exist also?

" it can be easily shown to be highly probable: like all existential statements, it is in an infinite (or sufficiently large) universe almost logically true,"
Isn't he just speculating on the multiverse theory that postulates an infinite number of copies of You exists. This can make the logical conclusion that a probable copy of You exist also? — ovdtogt

https://en.wikipedia.org/wiki/Possible_world

I don't think you've quite understood my argument. I am not postulating on 'possible worlds' but on the existence of an infinite number of Universes.

don't think you've quite understood my argument. I am not postulating on 'possible world' but on the existence of an infinite number of Universes. — ovdtogt

Yeah I got that. Popper was talking about "possible worlds" in the context of modal logic though.

Yes. Well that would not work as all 'possible worlds' would still have to adhere to the basic laws of physics.

Yes. Well that would not work as all 'possible worlds' would still have to adhere to the basic laws of physics. — ovdtogt

The whole talk about "possible worlds" isn't an ontic claim, here.

Philosophy seems to me to be the science of understanding what the hell someone else is talking about.

Thanks Ying for taking the trouble to post Popper's argument. A couple of things:

1. Popper means by testable that a theory can be disproved and by verifiable that a theory can confirmed. I used th word "confirmed" and not "proved" as I think doing the reverse would have invited Popper's disapproval for the reason that scientific reasoning is, at its foundations, inductive.

2. Popper wants to base science on empirical propositions which he defines as falsifiable. He explicitly wants to remove verifiability and probabilistic confirmability as conditions for empirical propositions.

He does this by considering the claim for the existence of an incantation to raise the devil. Such a statement would be presumably false but untestable (unfalsifiable) and have a high likelihood of being true IF we consider possible worlds. With one example he undermines the relationship between the empirical and the verifiable, between the empirical and probability; leaving only falsifiability as a criterion for empirical claims.

I think Popper is basically concerned about induction - the lifeblood of science. Verifying scientific theories though important don't provide us with certainty since no finite sample of past verifications is representative of the infinite future. Given this is so, we must look elsewhere for certainty and this can be found easily in falsifiability, a tool that can positively identify false theories.

Another thing to consider the combination of concepts with regard to statements that are presumably false, only verifiable and highly probable. I've underlined the most important aspect of the combination in statements like the claim that an incantation exists that can invoke the devil. There is the possibility that such statements are false. This undermines the utility of both verifiability and probability to identify empirical statements. That leaves us with falsifiability alone as the only reliable method for empirical claims.

What say you?

Popper might have done better to have restricted the notion of an empirical proposition to one whose domain of realisation is finite and closed rather than open and potentially infinite. That way he could have treated scientific laws and the demon summoning example uniformly and symmetrically, by saying that both lack empirical content - the former in not being verifiable in requiring infinite confirmation, and the latter in not being falsifiable in begging potentially infinite consideration.

In my opinion, it is better to require empirically meaningful propositions to be decidable, i.e to be both potentially verifiable and to be potentially falsifiable, which requires of the proposition in question to have finite extent.

Any universal proposition of the form "ALL X's have property Y", where the domain of the 'proposition' is potentially infinite, should be regarded as a pragmatic statement of scientific policy for guiding decision making rather than to be a proposition describing potential scientific fact.

That way he could have treated scientific laws and the demon summing example uniformly and symmetrically, by saying that both lack empirical content - the former in not being verifiable in requiring infinite confirmation, and the latter in not being falsifiable in begging potentially infinite consideration. — sime

I think verifiability is limited in scope to a particular world for the reason that induction isn't conclusive in any world. However for the devil-proposition to work the way Popper wants we need possible worlds (infinite "consideration" as you put it).

Popper uses the devil-proposition to emphasize the problematic combination of false AND untestable BUT verifiable. By definition verifiability is incapable of disproof and untestabiltity, well, relieves the lookout of his duty to spot the black swan in Australia.

<>

Thanks Ying for taking the trouble to post Popper's argument. — TheMadFool

No problem. :)

I think Popper is basically concerned about induction - the lifeblood of science. — TheMadFool

My understanding is that Popper rejected induction, and saw science as being a combination of abduction (conjecture and prediction) and observation. Failure to observe the predicted outcomes of a theory constitutes falsification which leads to refutation of the theory.

Induction is reduced to just the (ungrounded?) expectation that nature will continue to behave in the ways it has been observed to behave in the past.

My understanding is that Popper rejected induction, and saw science as being a combination of abduction (conjecture and prediction) and observation. Failure to observe the predicted outcomes of a theory constitutes falsification which leads to refutation of the theory.

Induction is reduced to just the (ungrounded?) expectation that nature will continue to behave in the ways it has been observed to behave in the past. — Janus

I see. I think you're in agreement with Popper regarding the necessity for falsifiability for a theory/proposition to be considered as scientific.

In Popper's argument he makes a distinction - that between verifiability and falsifiability. The meat of his argument lies in understanding this distinction.

You rightly pointed out that the scientific method in re falsifiability involves the following simple argument:

1. If theory A is true then the predictions X, Y, Z must be true
2. Predictions X, Y, Z aren't true
Ergo
3. Theory A is false

So we have a theory A that makes predictions that are falsifiable and this form of the scientific method agrees with Popper's falsifiability criterion.

As I said before Popper sees verifiability and falsifiability as two distinct concepts. I can't see the difference in the way you described the scientific method. I see verifiability and falsifiability as two sides of the same coin.

In the example I gave above, theory A is verifiable because of the predictions it makes but the fact that these predictions can turn up false means falsifiability is built into the principle of verifiability.

Perhaps if we look at Popper's argument more carefully we can see why he considers verifiability as not the same as falsifiability.

Propositon B = there exists an incantation that can invoke the antichrist.

B can be "verified". Verification here is the logical positivist notion of considering propositions meaningful only if and also just by its possibility of being perceived through the senses. Of course if we consider the scientific method as you described it (theories with predictions which when not observed falsifies the theory) then verifiability alone is sufficient because falsifiability is just the application of modus tollens to the argument.

However, Popper thinks B can't be falsified. Unfortunately he doesn't give us a reason why but only repeats himself 3 times. Is it because he's arguing in the context of all possible worlds, one of which would possess a working devil-invoking incantation or does he mean something else? If he is using all possible worlds to show B can't be falsified then he must mean that scientific theories need to be propositions about this and only this world; a world in which verifiability and falsifiability would be tied together like so: Verifiable if and only if falsifiable..

The way Popper uses probability - the fact that if all possible worlds are considered the existence of a devil-invoking incantation becomes highly probable - suggests that he is saying that all possible worlds make statement B unfalsifiable. He mentions in the beginning that he wants to discuss a purely existential proposition which I think means one whose scope is all possible worlds.

Popper thinks that despite the notion of falsifiability being implicit in verifiability it needs to be made explicit so that we may exclude propositions that have as a scope all possible worlds.

Kindly comment on this. Thanks.

Moreover, it can be easily shown to be highly probable: like all existential statements, it is in an infinite (or sufficiently large) universe almost logically true, to use an expression of Carnap's. — Popper

Yeah I got that. Popper was talking about "possible worlds" in the context of modal logic though. — Ying

The whole talk about "possible worlds" isn't an ontic claim, here — Ying

I think it's pretty clear that he is making an ontic claim - he says so himself (it's a "purely existential" statement). He is tilting against the windmill of probabilistic confirmation, and I don't see how modal logic could possibly help him in that.

I think it's pretty clear that he is making an ontic claim - he says so himself (it's a "purely existential" statement). — SophistiCat

What? The claim that the universe is infinite/sufficiently large? He's not referring to that. He's saying that the devil summoning thing, "like all existential statements", "in an infinite (or sufficiently large) universe" is "almost logically true". He also states that, "according to my criterion of demarcation it is excluded as non-empirical and nonscientific or, if you like, metaphysical...". He's highlighting a problem with the logical positivist account of demarcation (verification principle), which he hopes to sidestep with his own criterion ("I hope this example will also provide a reply to the often repeated criticism that it is perverse to exclude purely existential statements from empirical science and to classify them as metaphysical").

He is tilting against the windmill of probabilistic confirmation, and I don't see how modal logic could possibly help him in that.

Sure (not being sarcastic. here). In any case, I was talking to ovdtogt, who stated:

Isn't he just speculating on the Multiverse theory that postulates an infinite number of copies of You exists. This can make the logical conclusion that a probable copy of You exist also?

and:

I am not postulating on 'possible worlds' but on the existence of an infinite number of Universes.

which isn't what Popper was talking about.

What? The claim that the universe is infinite/sufficiently large? He's not referring to that. He's saying that the devil summoning thing, "like all existential statements", "in an infinite (or sufficiently large) universe" is "almost logically true". — Ying

Yes, and I don't see how this is a modal argument (the size of the universe wouldn't be relevant for that). His language here is sloppy, but he is, I think, alluding to something like a Boltzmann Brain situation, where through a random fluctuation of particles it could happen that certain words are spoken, immediately followed by something like a "devil" materializing in the vicinity. In a large enough universe, so the argument goes, this is almost certain to happen somewhere, some time, thus providing a specious verification for the existential claim. As it happens, though this wasn't what Popper had in mind, a multiverse (the actual, not the modal kind) would have served just as well for his argument.

Yes, and I don't see how this is a modal argument (the size of the universe wouldn't be relevant for that). His language here is sloppy, but he is, I think, alluding to something like a Boltzmann Brain situation, where through a random fluctuation of particles it could happen that certain words are spoken, immediately followed by something like a "devil" materializing in the vicinity. In a large enough universe, so the argument goes, this is almost certain to happen somewhere, some time, thus providing a specious verification for the existential claim. As it happens, though this wasn't what Popper had in mind, a multiverse (the actual, not the modal kind) would have served just as well for his argument. — SophistiCat

:up:

Verifying scientific theories though important don't provide us with certainty since no finite sample of past verifications is representative of the infinite future. — TheMadFool

Here's a parallel in Sextus Empiricus' Outlines of Pyrrhonism:

"Before the founder of the sect to which you belong was born, the argument which you propose in accordance with it had not appeared as a valid argument, but was dormant in nature, so in the same way it is possible that its refutation also exists in nature, but has not yet appeared to us, so that it is not at all necessary for us to agree with an argument that now seems to be strong."

1. If theory A is true then the predictions X, Y, Z must be true
2. Predictions X, Y, Z aren't true
Ergo
3. Theory A is false — TheMadFool

The only quibble I have with this-and it isn't substantive- is that I would have said "predictions X, Y, Z would be observed".

As I said before Popper sees verifiability and falsifiability as two distinct concepts. I can't see the difference in the way you described the scientific method. I see verifiability and falsifiability as two sides of the same coin.

In the example I gave above, theory A is verifiable because of the predictions it makes but the fact that these predictions can turn up false means falsifiability is built into the principle of verifiability. — TheMadFool

I think the issue here is that the idea of invariance is taken for granted in theories. So, any theory about the way nature is has a built-in assumption that nature is invariant, and thus one properly confirmed instance where predicted outcomes are not observed is enough to falsify and thus refute the theory.

The same doesn't hold for verification, though, because the observed outcomes might be anomalies due to some unknown factor, or nature might turn out not to be invariant; that is it might suddenly change its behavior, which means no theory can ever be unequivocally verified.

:up: :ok:

The only quibble I have with this-and it isn't substantive- is that I would have said "predictions X, Y, Z would be observed — Janus

What's the difference between my "predictions X, Y, Z must be true" and your "predictions X, Y, Z would be observed" ?

I do find the shift in meaning to be in better alignment with Popper though. I feel "verifiabilty" is expressed better with "would be observed than "would be true". The former is closer to Popper's views on the matter as the rationale of the scientific method isn't as logically restricted as in non-empirical arguments.

In non-empirical arguments, modus ponens and modus tollens works because the antecedent and the consequent are truth claims.

However the scientific method is a different beast. To continue with my example and your suggestion to use "would be observed rather than "would be true", I'd like to correct the scientific method to:

1. If theory A is true then prediction X, Y, Z would be observed.

2. predictions X, Y, Z are NOT observed.

So,

3. Theory A is false?!

The above argument looks ok but actually has a flaw in that when predictions fail to materialize (aren't observed) it doesn't always mean the theory in question is false. Take for example the classic case: All swans are white. If you fail to observe white swans it doesn't mean that the claim is false. It just means that you haven't discovered evidence for the claim. The only way we can say that the claim, all swans are white, is false is by observing a non-white swan. The modus tollens fails to apply like it does in non-empirical arguments.

This then would necessitate some experiment that is designed specifically to falsify a scientific theory.

I think this squares with Popper's view that verifiability alone doesn't qualify a theory as scientific. There has to be a way (experiment/observation) to falsify a theory.

Why is falsification more important than verification to Popper? I think the reason has to do with induction failing to provide definitive truth. If we are to put our trust in a theory it can't be based on it being true because the nature of induction only allows for tentative truth. Ergo we need a better spot to park our trust in and that spot is when we know a theory is NOT false which leads to Popper's falsifiability interpretation of science.

What do you think?

The above argument looks ok but actually has a flaw in that when predictions fail to materialize (aren't observed) it doesn't always mean the theory in question is false. Take for example the classic case: All swans are white. If you fail to observe white swans it doesn't mean that the claim is false. It just means that you haven't discovered evidence for the claim. The only way we can say that the claim, all swans are white, is false is by observing a non-white swan. — TheMadFool

This one example doesn't work. If one fails to see any swans period, then the proposition of "all swans are white" is no better than "all unicorns are white" - and there are no grounds to believe that swans are real (much less that they're only white) due to the proposition being unfalsifiable (here simplifying things by not introducing reasoned conclusions, such as could apply to the probability of alien life). However, if one does observe swans but fails to see a white swan, then the proposition is falsified.

Can't think of a different example to substantiate the claim you want to make. Maybe you can?

Why is falsification more important than verification to Popper? I think the reason has to do with induction failing to provide definitive truth. If we are to put our trust in a theory it can't be based on it being true because the nature of induction only allows for tentative truth. — TheMadFool

I think the underlined portions miss the mark. Truth is, but appraising when it is is not something that can be done with what others term absolute certainty. For as long as a falsifiable theory is not falsified, it can well be true - in an ontically determinate way. But since our subjectivity is not 100% objective (this being shorthand for a long-winded argument - my bad), we can't subjectively know with absolute subjective certainty that every instantiation of what we deem to be true (personally or collectively) actually is in fact true. However, if that addressed is falsifiable and if we are unable to falsify it despite our best attempts, then it gives all indications of in fact conforming to that which is ontic (else, of accurately corresponding to that which is real), i.e. of being true.

To this effect, hypothesize that a falsifiable proposition or theory is impossible to falsify both in practice *and* in principle. By what reasoning could one claim that this proposition or theory holds any chance of being untrue?

So, I think that we trust falsifiable theories that have not been in any way falsified precisely because we expect them to be true.

I agree with the general gist of your arguments so far, btw.

This one example doesn't work. If one fails to see any swans period, then the proposition of "all swans are white" is no better than "all unicorns are white" - and there are no grounds to believe that swans are real (much less that they're only white) due to the proposition being unfalsifiable (here simplifying things by not introducing reasoned conclusions, such as could apply to the probability of alien life). However, if one does observe swans but fails to see a white swan, then the proposition is falsified.

Can't think of a different example to substantiate the claim you want to make. Maybe you can? — javra

I was worried about that and was hoping someone would come up with something better.

Let me cheat and use categorical logic to show that indeed I am, very surprisingly to me, right.

All swans are white in logic doesn't have existential import unlike its negation: Some swans are black which can only be true if and only if there is at least one black swan.

Lacking claims of existence the proposition: All swans are white, is true even if you never saw a swan let alone white swans. I think in predicate logic the statement gets translated as:

IF x is a swan then x is white. Emphasis on "if".

However, if that addressed is falsifiable and if we are unable to falsify it despite our best attempts, then it gives all indications of in fact conforming to that which is ontic (else, of accurately corresponding to that which is real), i.e. of being true. — javra

This makes sense. Ok.

To this effect, hypothesize that a falsifiable proposition or theory is impossible to falsify both in practice *and* in principle. By what reasoning could one claim that this proposition or theory holds any chance of being untrue? — javra

Aside from a contradiction in your statement which I expect to carry some deep meaning I'll focus on the words "impossible to falsify". Such statements would be metaphysical for Popper, right?

Let me cheat and use categorical logic to show that indeed I am, very surprisingly to me, right.

All swans are white in logic doesn't have existential import unlike its negation: Some swans are black which can only be true if and only if there is at least one black swan.

Lacking claims of existence the proposition: All swans are white, is true even if you never saw a swan let alone white swans. I think in predicate logic the statement gets translated as:

IF x is a swan then x is white. Emphasis on "if". — TheMadFool

This thread is about empirical knowledge, I presumed, not axiomatic claims. Aside from which, how would "all unicorns are white" not be a true statement given the system of logic you're presented?

Aside from a contradiction in your statement which I expect to carry some deep meaning I'll focus on the words "impossible to falsify". Such statements would be metaphysical for Popper, right? — TheMadFool

OK, too brief in the expression. No contradiction intended. What I was addressing is a proposition that is epistemically falsifiable but not ontically falsifiable. This presumes that our knowledge is imperfect. To better illustrate via example: I say "all swans are either black or white" while holding imperfect knowledge of the world; I could falsify this claim by observing a red swan in some remote location; so its epistemically falsifiable. However, reality has it (here assuming a perfect knowledge of the world) that only black and white swans exist. So no matter how much I - the one with fallible knowledge - look in attempts to falsify this proposition, I will never be able to. Because only black and white swans exist, the proposition is not possible to falsify ontically.

This state of affairs is what makes the following understandable:

However, if that addressed is falsifiable and if we are unable to falsify it despite our best attempts, then it gives all indications of in fact conforming to that which is ontic (else, of accurately corresponding to that which is real), i.e. of being true. — javra

This thread is about empirical knowledge, I presumed, not axiomatic claims. Aside from which, how would "all unicorns are white" not be a true statement given the system of logic you're presented? — javra

Yes. This is about empirical claims. However, if there's an empirical claim worth the effort it has to be universal in scope i.e. should take the form "All A are B" which I believe must be logical much much before it can be empirical.

Let's take an empirical claim such as: All objects obey the laws of gravity. Notice that it is a Aristotelean categorical statement. Isn't it necessary then to consider the logical character of such statements before we talk of its empirical import? What do you think?

OK, too brief in the expression. No contradiction intended. What I was addressing is a proposition that is epistemically falsifiable but not ontically falsifiable. This presumes that our knowledge is imperfect. To better illustrate via example: I say "all swans are either black or white" while holding imperfect knowledge of the world; I could falsify this claim by observing a red swan in some remote location; so its epistemically falsifiable. However, reality has it (here assuming a perfect knowledge of the world) that only black and white swans exist. So no matter how much I - the one with fallible knowledge - look in attempts to falsify this proposition, I will never be able to. Because only black and white swans exist, the proposition is not possible to falsify ontically. — javra

I'd like some clarification on this "ontically falsifiable" and "epistemically falsifiable" categories.

All that falsifiability requires is that any given a scientific theory should have a built in mechanism that can look for evidence to falsify it.
.
If a scientific theory is categorically true then it is ontically unfalsifiable and the only way we can know that is to show that it's epistemically unfalsifiable.

In my opinion the argument is:

1. If ontically unfalsifiable then epistemically unfalsifiable
Ergo
2. If epistemically falsifiable then ontically falsifiable

That's to say all we need to work with is epistemic falsifiability to get to the truth i.e. ontic unfalsifiability.

Let's take an empirical claim such as: All objects obey the laws of gravity. Notice that it is a Aristotelean categorical statement. Isn't it necessary then to consider the logical character of such statements before we talk of its empirical import? What do you think? — TheMadFool

While I find a sharp distinction between rationalism and empiricism specious - Kant gave good examples of why this is, imo - the only way to substantiate the claim that you give is empirically, hence inductively. Its truth cannot be derived merely from axioms.

If a scientific theory is categorically true then it is ontically unfalsifiable and the only way we can know that is to show that it's epistemically unfalsifiable. — TheMadFool

The underlined portion doesn't work. That's the thing to induction: it can't evidence something with absolute certainty, which our empirical propositions and theories most often implicitly purport. For instance, "All swans are white" explicitly states a determinate state of affairs as though it were an absolute certainty - that it isn't an absolute certainty remains implicit.

Because we cannot ever show that an empirical claim is ontically unfalsifiable, it will always remain epistemically falsifiable to us. This even if it happens to be "categorically true", in which case it would be ontically unfalsifiable. The best we can do is not be able to falsify it in practice despite trying to - while never knowing if it can be falsified in principle. Not being so able, in turn, substantiates the belief that the claim is true.