I'd suggest that here truth is foundational, and knowledge derivative. — Banno

I'm not sure whether you are talking logic or child development here. But it seems to me that, from a child development perspective, this must be right. The development of empathy in small children has been much studied - admittedly the primary focus is on emotional empathy, but awareness of the different perspectives of other people (emotional and cognitive) is included. The philosophical relevance is that this is where the concept of knowledge becomes necessary for understanding what people do - or don't do. (Belief, it seems to me, must come later.)

I'm not sure whether you are talking logic or child development here. — Ludwig V

Logic. But I'm thinking of Davidson here, too - interpretation and the principle of charity fit in with your comments regarding empathy...

Belief only makes sense against a background of truth; it is, after all, what is thought true as opposed what is actually true.

Introspection is not immune from mistakes, because it is most always inferential. That one experiences what one presently experiences is, on the other hand, a brute given. — javra

H'm. I can see that one might use the words in those ways. But I would have called what you call the brute given, what I know by introspection, and called what you call introspection ordinary knowledge. But there is a fuzzy line between the experience of pain and the interpretations of pain (as caused by falling down or whatever). My doubts about what you are saying are around the fact that what you call he "brute given" is only by extension something that I know about. That requires me to distance myself from the experience itself and think about it in a way quite different from the simple reaction ("Ouch!"), which does not mean "I am in pain", which requires conceptualization.

As one very common example, visual experiences that occur during REM periods of sleep are all seen with the mind’s eye. So then people can’t say, “I saw X in a dream last night”? Yet this is common practice. — javra

I think the practice is all right. When I say "I saw X in a dream", I defuse the standard meaning of "see" by adding "in a dream". That signals that I'm aware that I didn't "really" see X. (Contrast the small child who wakes up in the middle of the night terrified by the wolves all round the house.)

Logic. But I'm thinking of Davidson here, too - interpretation and the principle of charity fit in with your comments regarding empathy... — Banno

Yes. That's not an accident. But what I'm especially interested in is, put it this way, the glitches in natural language that require us to develop or learn conceptual dodges that enable us to cope. My reply to @J earlier (bottom of last page) is a nice example. It's in a grey area between logic and psychology, but it is where, IMO, the later Wittgenstein is operating. The Blue Book is an excellent example, just because he is developing his methodology.

Belief only makes sense against a background of truth; it is, after all, what is thought true as opposed what is actually true. — Banno

That's true. But it requires, not just introspection, but an awareness of other people as different in certain ways. Arguably, that awareness is even essential to self-awareness and introspection beyond what Wittgenstein calls expressions in his discussion of pain, as in " the verbal expression of pain replaces crying, it does not describe it" (PI 244) and "How can I even attempt to interpose language between the expression of pain and the pain?" (PI 245.

I don't quite understand this. Our community ascribes false beliefs to people all the time and that's why they are called "intentional" — Ludwig V

And that is the idea I am attacking. Supposedly, Intentionality refers to "The quality of mental states (e.g. thoughts, beliefs, desires, hopes) which consists in their being directed towards some object or state of affairs." - Google Gemini

So according to this definition of intentionality, the intentionality of a mental state has nothing to do with the opinions and linguistic biases of a community, and concerns a genuine, real relationship between a believer and an object that his beliefs are directed towards. But if this relationship is a causal relationship between the object of the belief and the mental state of the believer, then how is a false belief possible?

Notice that we don't attribute false beliefs to a glitchy measurment device - rather we refer to the device as uncalibrated or not functioning in accordance with its specification. And so we don't consider measurement error as as an attribute of the state of the measuring device; rather we consider the device as not functioning in accordance with our wishes, in that it is us who chooses the "truthmaker" of what we want the device to be measuring. And hence we do not attribute intentionality to the state of the device with respect to our desired truthmaker.

The situation isn't different with humans as measuring devices. And hence as with the example of a thermometer, either humans have intentional belief states, in which case their beliefs cannot be false due to the object of their beliefs being whatever caused their beliefs, else their beliefs are permitted to be false, in which case the truthmaker of their belief is decided externally by their community.

Truth conditional semantics does not escape the dilemma between the postulation of belief intentionality ,causal semantics and trivialism on the one hand, versus the postulation of false beliefs and community decided truthmakers on the other, but illustrates how the dichotomy is muddied in actual linguistic practice through a process of biased radical translation.

On the one hand, a radical translation of a speaker's utterances in terms of truth-conditional semantics, interprets the speaker's utterances as denoting statistical correlations between his mental state and his external world (charity). But on the other hand, the radical translator gets to decide the cases when the speaker's utterances are supposedly "false" (uncharity), in accordance with the translator's personal agenda, as opposed to in terms of the actual causes of the speaker's utterances when he said the "wrong" thing.

Davidson's proposal is scientifically useful but non-philosophical and aligns with how the concept of "beliefs" are used practically and non-seriously in AI and machine learning, especially in the case of Bayesian reinforcement learning when we callibrate a neural network's responses to the external states of the environment and call the resulting neuron activations "beliefs" (which denote our wishes). But Davidison, like machine learning, ducks the philosophical question as to how to rehabilitate epistemology, given that any realist notion of beliefs seems untenable.

Maybe this is a good way to frame the problem in terms of JTB:

Do I have to know that X is true in order to use it as the T in a JTB statement? Is that knowledge the result of a previous application of JTB? etc. I know you think this can be dissolved, but I still don't see how. Truth is certainly foundational to the whole set-up, I agree, but the question seems to be whether I have to know that X is true. We can loosen that requirement, and say that "X is true" is pre-JTB and therefore not a knowable instance of truth. This seems to resemble more closely our actual practice.

I cannot justify that I have that knowledge to you, if you believe me you take it on faith. — Janus

Agreed. I think we're speaking of self-justification here. Can you justify to yourself that "I am thinking X" is necessarily true? This starts to become merely verbal, depending on what sort of thing you think a justification is. Self-evidence, on some accounts, requires a justification, or at least an explanation. On other accounts, it's the very thing that obviates justification. Does it much matter which construal we pick? What matters is the concepts in play, not our terms for them.

But your description is excluding the "straightforward" answer that the drunk is hallucinating a pink elephant. — Ludwig V

That was kinda deliberate. For what is a hallucination, and how do we talk about it? Is there an obvious consensus? Some would describe hallucinating as "seeing something that isn't there"; others would describe it as "thinking you see something that isn't there". Is there a meaningful difference, apart from choice of terms?

In a sense, of course, it just kicks the can down the road, — Ludwig V

Precisely, as I just described. But the can isn't important, in my opinion, so this shouldn't bother us.

Do I have to know that X is true in order to use it as the T in a JTB statement? — J

Under the strongest possible interpretation of truth-conditional semantics (the principle of maximal charity), the meaning of your use of a sentence S refers to the actual cause of your use of S; in which case, the answer to your question is vacuously yes, because the truth of your utterance of S is necessarily true when your utterance of S has been correctly understood.

On the other hand, if the community gets to decide the truth-maker of your use of S irrespective of whatever caused you to utter S (the principle of minimal charity), then you cannot know that S is true until after you have used S and received feedback. In which case, the truth of S isn't a quality of your mental state when you used S.

Under the strongest possible interpretation of truth-conditional semantics (the principle of maximal charity), the meaning of your use of a sentence S refers to the actual cause of your use of S; — sime

John points to the white board, which has the figure 2 written on it. He says, "That is a prime number." We'll call the sentence he uttered S.

The cause of his use of S is a factor in determining the truth conditions. That cause is not the truth conditions, though. Or if it is, how?

On the other hand, if the community gets to decide the truth-maker of your use of S irrespective of whatever caused you to utter S (the principle of minimal charity), then you cannot know that S is true until after you have used S and received feedback. In which case, the truth of S isn't a quality of your mental state when you used S. — sime

"Truth-maker of your use of S" doesn't make sense to me. What are you talking about?

Like @frank, I'm not sure I get this. "That is a prime number" is true (or false) regardless of what John thinks about it. The question is, How confident can he be that he knows which is which? Of course there are fuzzy cases, but let's just consider this straightforward one. Isn't he trying to bootstrap himself into a JTB?

I think JTB is a characterization of internalism..

"That is a prime number" is true (or false) regardless of what John thinks about it. The question is, How confident can he be that he knows which is which? — J

If he read Descartes' Meditations, he would be cautious about knowledge claims. If he asserts things in spite of Descartes, he could say he's secretly prefacing the assertion with "If the Evil Demon isn't tricking me right now, ..."

My doubts about what you are saying are around the fact that what you call he "brute given" is only by extension something that I know about. That requires me to distance myself from the experience itself and think about it in a way quite different from the simple reaction ("Ouch!"), which does not mean "I am in pain", which requires conceptualization. — Ludwig V

Infants and nonhuman lifeforms do not have the conceptual power to articulate “I am in pain”. Yet, I so far presume, we’d both agree that they can yet experience pain. It is this which is knowledge-by-acquaintance, this for any awareness-endowed being, which, again, is in no way JTB: it is a known that is neither dependent on any type of justification nor does it require an upheld belief (a belief of what one experienced can follow the experience itself, but one does not ubiquitously first believe X in order to next experience it). It is merely a true immediate experience. One thereby knows what one directly and immediately experiences consciously—such as pain or pleasure, or color, size, and shape, or tactile texture, or such and such thought, and so forth—only by direct acquaintance. Not by conceptualizations utterly devoid of any direct acquaintance. We non-infant humans then make use of conceptualizations to express these instances of knowledge-by-acquaintance via words, which embody concepts, and can then further cognitively manipulate these concepts. But the knowing that one is in pain rather than in states of pleasure, for one example, remains a JTB-devoid knowledge-by-acquaintance—this just as much for an adult human as for a nonhuman animal.

As reference to the philosophical usage of the term, as previously provided, here is the SEP article on knowledge by acquaintance.

I think the practice is all right. When I say "I saw X in a dream", I defuse the standard meaning of "see" by adding "in a dream". That signals that I'm aware that I didn't "really" see X. — Ludwig V

I understand this, which is why the second example was provided. Just checked, and “to form a mental picture of” is an official definition of the term “see”. So as far as I can tell, in standard English, one can really see an imagined object. Besides, when the drunkard sees a pink elephant, the drunkard supposedly does not yet know in a JTB sense whether the elephant is a mental picture or else a real aspect of the external world. He merely witnesses via visual phenomenological means a pink elephant—one which, as previously expressed, might not be real or else might in fact be real, depending on context. (For example, I’m fairly sure there are drunkards in Indian festivities where pink power can be thrown on top an elephant, thereby resulting in the drunkard seeing a real elephant which is pink in appearance.)

All good. Self-awareness requires awareness of others, such that they develop together, that you and I are aware differently.

I'm not convinced that Wittgenstein accepted JTB, in the way @Sam26 seems to think. I read him in On Certainty more as pointing out that if we do accept JTB then these are the consequences - there are for instance things that we might casually say we know that are rules out as knowledge by the JTB account. We can't know how a dog that has been run over feels.

Do I have to know that X is true in order to use it as the T in a JTB statement? — J

No. But it has to be true. This was my first reply to you in the present conversation:

Seems to me that folk read JTB as the claim that in order to know something, we must know that it is true. It's hard to get across that this is not what the JTB account is saying. It's not that the proposal is justified, believed and known to be true, but that it is justified, believed and true. — Banno

Agreed. I think we're speaking of self-justification here. Can you justify to yourself that "I am thinking X" is necessarily true? — J

When I think X or feel a sensation, there can be no doubt about it. So, I see no need for justification. Justification is only for beliefs, not for those things known with certainty. (Note: I leave out of consideration the kind of radical skepticism that Descartes feigned, simply because I think it is always a matter of feigning.

Justification is only for beliefs, not for those things known with certainty. — Janus

OK, that seems like a good way to look at it, with perhaps the caveat that it's reasonable also to ask, "Why are you certain?" or "What makes you rely on this experience?" (similarity to previous ones, presumably). These aren't requests for justifications in the same way that asking for a justification of a belief is, but their aim is to ask for an account, a rationale. I can't simply reply, "Well, I just do." This rarely comes up, of course, but it's worth noting.

Also, you can say that Descartes "feigned" skepticism, but he wasn't trying to fool himself or others. He wasn't just being annoying. He was trying to pursue a method he believed would lead, by elimination, to clear and certain knowledge.

OK, that seems like a good way to look at it, with perhaps the caveat that it's reasonable also to ask, "Why are you certain?" or "What makes you rely on this experience?" (similarity to previous ones, presumably). — J

Cheers, that's a fair question—and I hope I can answer it to your satisfaction. I take it that possession of knowledge obtains when there can be no doubt. For example, when I am looking at something there can be no doubt that I am looking at that thing. When I am doing something there can be no doubt that I am doing that thing. Same with feeling and thinking.

The problem that I have with the idea of knowledge being defeasible is that if it isn't true it isn't knowledge, so if what I think I know is possibly false, then I don't really know it—so I say instead that I believe it and that it is belief, not knowledge, which is defeasible.

As to Descartes, I understand his skepticism to be methodological—an attempt to determine what it is possible for him to doubt. The problem I have is that he doubts things on the mere logical possibility that he might be deceived by an Evil Demon. I think such doubt is absurd. I agree with Peirce:
"Let us not pretend to doubt in philosophy what we do not doubt in our hearts" .

The problem I have is that he doubts things on the mere logical possibility that he might be deceived by an Evil Demon. — Janus

This may seem like quibbling, but he doesn't actually doubt things. He points out that it would be possible to doubt them. Of course he knows that no sane person is going to doubt most of their own experience, but that doesn't satisfy his Method. He wants the grand prize -- absolute certainty, beyond even the possibility of doubt. I personally feel that we don't need that in order to do metaphysics and epistemology; Descartes disagreed, hence his Method. But we really shouldn't see him as raising "philosophers' doubts" for the sake of skepticism. He detested skepticism and believed he had refuted it. (And we have a perfectly good modern version of the Evil Demon: the "Matrix hypothesis.")

OK. Bear with me. Let's say I'm in a "JTB situation"; that is, I want to find out whether I possess a piece of knowledge. Will the justifications that I cite -- the J in JTB -- for why I believe X refer to the same sorts of facts that, out in the world, would show whether statement X is true or false?

Example: X is "Taurize is a village in France." My justifications for believing X would be, let's say, "I've looked in a reliable atlas, and spoken to someone who's visited Taurize and confirms this." (And we could tighten this up ad infinitum, but you get the idea.) Now suppose I want to find out whether X is true -- whether Taurize really is a village in France. Would the facts necessary to do this be the exact same ones cited as my justifications for believing X? Are the two sets completely congruent?

But if this relationship is a causal relationship between the object of the belief and the mental state of the believer, then how is a false belief possible? — sime

It isn't. Which is why the relationship between the object of the belief and the mental state of the believer is not a causal relationship.

the intentionality of a mental state has nothing to do with the opinions and linguistic biases of a community, — sime

That's a very good point. But the object will be framed in a language, and that language will be the framework will have been learned from the community.

And hence as with the example of a thermometer, either humans have intentional belief states, in which case their beliefs cannot be false due to the object of their beliefs being whatever caused their beliefs, else their beliefs are permitted to be false, in which case the truth-maker of their belief is decided externally by their community. — sime

Well, the first option is not an option, so it must be the second. But it's not quite right to say that the truth-maker of specific beliefs is decided by the community. The community teaches us about truth and falsity and how to determine it in general. Individuals then apply that framework to specific cases; disagreements will be discussed within the community and, often but not always, an agreement will be reached. (Sometimes the belief will be one that is not determined by the shared rules.)

On the other hand, if the community gets to decide the truth-maker of your use of S irrespective of whatever caused you to utter S (the principle of minimal charity), then you cannot know that S is true until after you have used S and received feedback. In which case, the truth of S isn't a quality of your mental state when you used S. — sime

Not quite right. Given that I have learned how to determine truth and falsity, I can make a decision. I don't need feedback on each case. Nonetheless, the feedback that I receive is important in maintaining the framework that we have all learned. (It is not impossible for the community to be wrong.)

the question seems to be whether I have to know that X is true. — J

Yes and no. I think it is more accurate to say that the requirement of truth is a kind of absolute liability. I make my judgements, but they may turn out to be wrong later on. In that case, I have to withdraw my claim.

We can loosen that requirement, and say that "X is true" is pre-JTB and therefore not a knowable instance of truth. This seems to resemble more closely our actual practice. — J

It's true that we rarely consciously and specifically apply the JTB. It's a formalization of what (normally) we actually do in a messy, informal way. I don't understand what it would be for something to be "pre-JTB".

For what is a hallucination, and how do we talk about it? Is there an obvious consensus? Some would describe hallucinating as "seeing something that isn't there"; others would describe it as "thinking you see something that isn't there". Is there a meaningful difference, apart from choice of terms? — J

Asking the question "what is a hallucination?" in the sense that you seem to mean it presupposes that a hallucination is an object. It leads us to posit various other pseudo-objects as if they could magically explain away what puzzles us. But they can't. The whole point is that there is no object. But if you ask what leads us to say that someone is hallucinating, we look at what someone says and does - attributing a hallucination to them presents what's going on in a way we can understand. It is still puzzling and we look for explanations - there's no way round that.

He detested skepticism and believed he had refuted it. (And we have a perfectly good modern version of the Evil Demon: the "Matrix hypothesis.") — J

Very true. It is odd that there seem to be no philosophers who actually accept scepticism. They all try to explain it away or neutralize it. Mostly, other philosophers accept the destructive moment, but reject the constructive response.

He points out that it would be possible to doubt them. — J

The problem is that he does not consider what actual limitations there are on doubts, and reduces it to the possibility of saying "I doubt that..." in front of almost any proposition. But if we ask what the content, the reality, the significance, of the doubt is, we find nothing.

Let's say I'm in a "JTB situation"; that is, I want to find out whether I possess a piece of knowledge. Will the justifications that I cite -- the J in JTB -- for why I believe X refer to the same sorts of facts that, out in the world, would show whether statement X is true or false? — J

I think that the justifications are mostly the same sorts of facts that would show whether X is true or false. But there can be justifications to the effect that I am in a position, have the skills, to know - which are of a different kind or level.

I'm not convinced that Wittgenstein accepted JTB, in the way Sam26 seems to think. I read him in On Certainty more as pointing out that if we do accept JTB then these are the consequences - there are for instance things that we might casually say we know that are rules out as knowledge by the JTB account. — Banno

I don't think that JTB is the kind of thing that the later Wittgenstein would want to accept or reject - pointing out the consequences of acceptance and rejection and leaving us to make up our own minds is much more his style.

We can't know how a dog that has been run over feels. — Banno

I get the point. Applying JTB to a dog seems inappropriate, because the dog doesn't speak. As always with animals, applying our descriptions of what we know and feel to them needs to be done quite carefully. But I think we can attribute beliefs to dogs - and other animals, and we can ask how why they believe what they believe and assess whether their beliefs are true or not. The same applies to experiences - there's no doubt, IMO, that they feel pain, sometimes less and sometimes more. So I don't understand why you say this - unless you are thinking of our inability to know what it's like to be a bat.

I think that the justifications are mostly the same sorts of facts that would show whether X is true or false. But there can be justifications to the effect that I am in a position, have the skills, to know - which are of a different kind or level. — Ludwig V

Yes, I think so too. Let's see what @Banno says, and then I'll try to show where I'm going with this.

We can loosen that requirement, and say that "X is true" is pre-JTB and therefore not a knowable instance of truth. This seems to resemble more closely our actual practice.
— J
It's true that we rarely consciously and specifically apply the JTB. It's a formalization of what (normally) we actually do in a messy, informal way. I don't understand what it would be for something to be "pre-JTB". — Ludwig V

By pre-JTB I mean that we would enter the "JTB situation" already believing that X is true. Our belief in X is not a result of what is about to happen if we successfully apply JTB, hence not knowledge. The difference between believing and knowing is important here. If, in trying to determine whether I possess a piece of knowledge, I ask myself, "Is X true?" (a JTB requirement for knowledge), I can only reply, "I believe so." I can't say, "I know it is," because this initiates the vicious circle.

Asking the question "what is a hallucination?" in the sense that you seem to mean it presupposes that a hallucination is an object. — Ludwig V

I didn't mean it to. It can just as well be an activity or an event. We can still ask what it is, taking "is" in one of its many familiar usages. The question was whether there's a "correct way" to describe the activity of hallucinating using the word "see." I'm saying, no, it's terminological; "see" can work either way.

The problem is that he does not consider what actual limitations there are on doubts, and reduces it to the possibility of saying "I doubt that..." in front of almost any proposition. But if we ask what the content, the reality, the significance, of the doubt is, we find nothing. — Ludwig V

We've talked about this in the context of Williams' book on Descartes. I think you're being too harsh. If it should turn out that I am really a brain in a vat or a Matrix-bound person, then my doubt about the objective references of my experiences is well-founded. It's not merely a linguistic construct. Indeed, this possibility seems much more plausible to me than the Evil Demon! -- though still pretty unlikely. In any case, perhaps we've just set different "limitations on doubts," and what seems doubt-worthy to me, doesn't to you. But surely this kind of doubt signifies more than nothing, wouldn't you say? It's a thinkable thought, and not nonsense.

By pre-JTB I mean that we would enter the "JTB situation" already believing that X is true. Our belief in X is not a result of what is about to happen if we successfully apply JTB, hence not knowledge. The difference between believing and knowing is important here. If, in trying to determine whether I possess a piece of knowledge, I ask myself, "Is X true?" (a JTB requirement for knowledge), I can only reply, "I believe so." I can't say, "I know it is," because this initiates the vicious circle. — J

I'm a bit confused by all this. Someone passes on to me a piece of information. Normally, I would just accept what I'm told because this informant is very reliable. But for some reason I decide to examine this claim more closely. So I set aside my assumptions including my belief that what I have been told is true. Then I ask myself the questions... Short story, anyone with any sense entering a "JTB situation" would and should set aside any assumptions that have already been made.
But there is a problem about the T clause. It is clear that it is not about what my informant knows or beliefs and ot about what I know or believe. Yet any verdict I give on the truth or not of the information is inescapably only what I know or believe. The effect - the significance - of the T clause, so far as I can see, is to require me (and not just my informant) to take responsibility for the truth of the information - to endorse it, in other words. As a result, my claim to knowledge continues to be vulnerable after I have made my decision; if it should turn out to be wrong, I will have to withdraw my claim. On the bright side, if my informant's justification was a bit dodgy, my claim will stand so long as no refutation appears.

The problem that I have with the idea of knowledge being defeasible is that if it isn't true it isn't knowledge, so if what I think I know is possibly false, then I don't really know it—so I say instead that I believe it and that it is belief, not knowledge, which is defeasible. — Janus

I think one defeats a claim to knowledge if it is false. Possibly false is far too strong and leads to us abandoning swathes of what we know quite unnecessarily. "possible" does not imply "actual".

It can just as well be an activity or an event. We can still ask what it is, taking "is" in one of its many familiar usages. The question was whether there's a "correct way" to describe the activity of hallucinating using the word "see." I'm saying, no, it's terminological; "see" can work either way. — J

Hallucinating isn't usually something that I do; it's something that happens to me. I think of it as an event or process. The point of the concept of hallucination is to allow us to recognize Macbeth's behaviour ("Is this a dagger I see before me?" etc. etc.) as what it is, the behaviour of someone who is seeing a dagger, but cancelling the actual dagger. Compare pretending or acting.
I think it is true that we can equally say that Macbeth is seeing something that isn't there or Macbeth thinks he sees something that isn't there. I would say that the first alternative suggests that there is some thing that he sees that isn't there and so I prefer the second option. `

We've talked about this in the context of Williams' book on Descartes. I think you're being too harsh. — J

Oh dear! My memories of that are, I'm afraid, a bit vague. Perhaps I am being too harsh. I would accept that there is a balance to be struck. But I am quite sure that not all possibilities are equally possible. The awkward bit is that the dividing line between them is not at all clear. There's possibilities like the ones that Eliza dreams about when she sings "wouldn't it be loverly" in My Fair Lady or we can be fascinated by like "Battle Star Galactica". I classify these as fantasies and I think they have only have significance for psychology or the philosophy of psychology. There's other possibilities like whether there is still honey for tea or the cream is still fresh. They do have significance for epistemology. Possibilities can change their status. Something that is a fantasy at one time can become a dream and ultimately a reality.

any verdict I give on the truth or not of the information is inescapably only what I know or believe. — Ludwig V

This is the nub, I think: It can never be what you know, only what you believe. Never, that is, without raising the specter of the vicious circle. Because to already know that the piece of information is true, that knowledge would have to have been verified via JTB. (This all assumes you think JTB is a good yardstick for knowledge, of course.)

I think it is true that we can equally say that Macbeth is seeing something that isn't there or Macbeth thinks he sees something that isn't there. — Ludwig V

Good. Seems that way to me too.

We've talked about this in the context of Williams' book on Descartes. I think you're being too harsh.
— J
Oh dear! My memories of that are, I'm afraid, a bit vague. Perhaps I am being too harsh. — Ludwig V

Harsh on Descartes, not me, I hasten to say; your forum manners are impeccable. As for vague memories . . . don't get me started. Aging is a fog, obscuring near and far.

This comes out in an anecdote related by Fania Pascal, who knew him in Cambridge in the 1930s:

I had my tonsils out and was in the Evelyn Nursing Home feeling sorry for myself. Wittgenstein called. I croaked: “I feel just like a dog that has been run over.” He was disgusted: “You don’t know what a dog that has been run over feels like.” — On Bullshit Harry Frankfurt

I continue to think there is a consideration of scope here that is missing from your account.

Notice that knowing is an attitude towards the proposition, hence the requirement that we set out who it is that is doing the knowing. So we want to get to "J knows that p".

According to the JYB account, we must have it that the following are all true:

1. J believes that p
2. p is justified
3. p

Notice that it is the belief that brings J. into the scope of the knowledge statement.

This, at least in part; since it is arguable - and I would argue - that the justification is also an attitude.

Notice that the last, "p", is not justified in any way, nor is it believed - it's just true. It is not about your "finding out" if p is indeed true.

Would the facts necessary (to find out whether X is true) be the exact same ones cited as my justifications for believing X? — J

Notice that you are not asking if p is true, but how you find out if p is true, and so again asking about an attitude. The facts that help you decide on your attitude are irrelevant to whether p is true or not.

So, is the idea that we can possess knowledge (i.e., possess beliefs that are justified and true) but we can never know that we possess knowledge (unless perhaps the object of knowledge is our own beliefs or experiences)?

If so, I suppose the idea that the act of understanding involves knowing that one knows what is understood would have to be abandoned. Presumably though, belief is still reflexive in this way. If one believes x, then one believes that one believes this.

Here is a wrinkle perhaps: if Macbeth cannot be certain about the (seemingly external) truth of what a knife is, how can he be certain that he sees a knife (regardless of if it is a hallucination or not)? If he cannot know that he knows what a knife is, then he can, at best, merely know that he believes he is experiencing a knife.

He wants the grand prize -- absolute certainty, beyond even the possibility of doubt. I personally feel that we don't need that in order to do metaphysics and epistemology; Descartes disagreed, hence his Method. But we really shouldn't see him as raising "philosophers' doubts" for the sake of skepticism. He detested skepticism and believed he had refuted it. (And we have a perfectly good modern version of the Evil Demon: the "Matrix hypothesis.") — J

I think absolute certainty is as impossible as radical doubt. You simply cannot doubt everything—somethings need to be taken for granted in order to doubt. I agree with you that we don't need absolute certainty in order to pursue metaphysics and epistemology—in fact in the case of metaphysics I would say there can be no certainty at all, that it all comes down to plausibility, because we are dealing with the non-cognitive.

I wasn't saying Descartes raised doubts for the sake of skepticism. Quite the opposite—he was after a degree of certainty which I think is impossible. The Matrix Hypothesis I think is absurd, because it posits that there is a real world in which the virtual world we inhabit is sustained, and this means the need for explanation is just pushed one step further back.

The problem that I have with the idea of knowledge being defeasible is that if it isn't true it isn't knowledge, so if what I think I know is possibly false, then I don't really know it—so I say instead that I believe it and that it is belief, not knowledge, which is defeasible.
— Janus
I think one defeats a claim to knowledge if it is false. Possibly false is far too strong and leads to us abandoning swathes of what we know quite unnecessarily. "possible" does not imply "actual". — Ludwig V

I would say that it we determine that something is possibly false then we don't at all need to "abandon it" but merely to abandon the pretense that we know it to be so, for the more modest claim that we believe it to be so. Why do we need to talk in terms of 'knowledge that' when nothing is lost by talking instead of 'justifiably believing that'?

Because to already know that the piece of information is true, that knowledge would have to have been verified via JTB. — J

If knowledge were a matter of accumulated atomic pieces, then you are right. But it isn't. We learn how to do colour and at least some of the colours at the same time, and elaborate from there. We learn about solid objects as we encounter them before we can even conceive of them. Then we can deal with individual solid objects as they crop up, whether we have encountered that specific kind before or not.

(This all assumes you think JTB is a good yardstick for knowledge, of course.) — J

Have you got a better candidate? I don't recall encountering one.

If he cannot know that he knows what a knife is, then he can, at best, merely know that he believes he is experiencing a knife. — Count Timothy von Icarus

Knowing what a knife is is only partly a question of knowing that it has a sharp edge and a handle. It also involves having the know-how to identify knives and distinguish them from spoons and swords. That requires input from other people, who have been teaching me what objects are and how to classify them since before I could speak.

It seems to me that he cannot know that he knows on his own. "I know that I know ..." is pure pleonasm. But it is an important feature of my attributing knowledge to someone that, by passing on the information that he knows, I endorse the knowledge. So "know" not only has space for endorsement by other people, it is built in to the concept as an unavoidable commitment. If I want to avoid commitment, I say that they believe that p. (If I actually disagree, I can say that they think that p.)

in fact in the case of metaphysics I would say there can be no certainty at all, that it all comes down to plausibility, because we are dealing with the non-cognitive. — Janus

If metaphysics is about the non-cognitive (which needs a bit more fleshing out), are we sure that certainty and plausibility even apply?

The Matrix Hypothesis I think is absurd, because it posits that there is a real world in which the virtual world we inhabit is sustained, and this means the need for explanation is just pushed one step further back. — Janus

Yes, that's right. In the case of the Matrix, it turns out that the real world is the same kind of world that the simulation places us in, so the fundamentals haven't changed. In fact, as we know, there is a case for saying that we already know that the real world is radically different from the world as we know it. No solid objects, everything consists of wavicles. What a nightmare!

Why do we need to talk in terms of 'knowledge that' when nothing is lost by talking instead of 'justifiably believing that'? — Janus

Well, if there were something to be gained, it might be a change worth making. But so long as we distinguish between true beliefs and false ones, the issues remain. But what are the issues? As I sit here, it is possible that a meteorite or similar is hurtling towards me and will land on my head. I could move and so avoid that disaster. But the possibility applies to anywhere else I might move to. So not only is the probability uncomputable and vanishingly small, but there is nothing I can do to avoid it - apart from living a mile underground, which would have its own limitations and dangers. So I take my cue from my society and ignore the possibility. I haven't been wrong yet.

I think these discussions usually leave out half the issue. If it is wrong to believe something that might not be the case, then, presumably, it is equally wrong not to believe something that is the case. The more cautious you are in avoiding false beliefs, the more you risk not accepting true beliefs. There's no safe territory. But surely to worry endlessly about possibilities that make no difference does not look like a particularly beneficial or even entertaining occupation.

I would say that it we determine that something is possibly false then we don't at all need to "abandon it" but merely to abandon the pretense that we know it to be so, for the more modest claim that we believe it to be so. — Janus

We can only pretend something that is possible. So if something is possibly false and we can pretend to know it, then it must be possible to actually know it.

This comes out in an anecdote related by Fania Pascal[/quote]
Thanks for the link. I shall read that soon - possibly today!
It sent me down the rabbit hole, wondering what it is to know what anything feels like and whether it is appropriate to read philosophical significance into what he said. He may have meant the remark simply as a kind of "buck up" reminder. That's something that is, perhaps, rather out of favour nowadays, but at the time, it was common place. I was brought up on "Worse things happen at sea". Once I grew up enough to wonder what the relevance was, it stopped working.
If it does have philosophical significance, we're in the territory of private experiences, aren't we? Wittgenstein doesn't think I know about them - at least not in the same sense that I know about the pain of others. Not because the truth is elusive, but because it is not clear that truth really applies to my responses to my own pains. So the idea that I can know what someone else knows when they are in pain seems - inappropriate. A topic for another discussion sometime.

The facts that help you decide on your attitude are irrelevant to whether p is true or not. — Banno

I take your point. Whether I believe that p and on what grounds is a matter that is entirely distinct from the question whether p is true. That distinction is important when I am considering the beliefs of other people. But when I ask myself whether I believe that p, surely I need to consider whether p? When I have decided whether p, I know whether I believe it or not. From my point of view, there are not two questions here, but only one.