Synthetic a priori = adds new content, but is knowable independently of experience.

That last category was Kant’s unique insight. Mathematics is built around it — “7+5=12” is not analytic, because “12” isn’t contained in “7+5,” but it’s still a priori. — Wayfarer

Let's slow down on this one. Kant doesn't speak about "content" in the [Prolegomena] (where the 7+5 example is discussed). He says that the concept of "12" is not the same as the concept of "7+5". According to him, we need an "intuition" ("perception" would probably be our way of saying it today) of the physical in order to discover "12". (He suggests that our five fingers, and then seven fingers, would do the trick.) "Hence our concept is really amplified by the proposition 7+5 = 12, and we add to the first concept a second concept not thought in it." What Kant regards as analytic here is the judgment that 7 and 5 must add up to some number -- but this does not tell us what particular number.

The place where this can be challenged, I think, is the reliance on intuition. If this is truly the case, don't we have to question whether the judgment is indeed a priori? Kant addresses this in Sec. 281: "How is it possible to intuit anything a priori?" I don't want to take this any farther, except to say that the case for math as a series of synthetic a priori judgments, even on Kant's own terms, is far from closed.

But Wittgenstein disagrees with Moore’s depiction of this form of certainty as a kind of empirical knowledge. — Joshs

Yes, that's a good link to Moore and Witt. In this context, I'm not so concerned to ask whether there is such a thing as direct knowledge -- or rather, I take it as given that there is. The problem is to explain what we mean by that, and what can count as a justification for our confidence in it. Witt, as I understand him, is raising a doubt not about the "knowledge" part, but about whether it is empirical. That's also what I was moving toward, in saying "If 'I am having thought X' needs a justification, we'd have to look elsewhere." Hinges and forms of life are good candidates.

I agree that when it comes to claims of knowledge, justification is required. On the other hand I know many things with certainty that require no justification simply because they are directly known―in these cases justification just doesn't enter the picture. — Janus

And this resembles the "A or ~A" case, where it's difficult to see it in terms of justifications. Still, I think the conclusion we ought to draw from this is that we're not quite sure what a justification is. What sorts of reasons may play a part in justification? (We noted earlier that a "good justification" is very unclear, in many cases.) If you ask me for my justification in believing "I am having thought X right now" and I reply, "I am directly observing this occurrence as we speak," have I offered a justification? Perhaps so; that's one way of understanding what reasons count as justification, though I'd probably also need to say something about the previous reliability of my direct observations. Or we might conclude that "directly observing" and "having" are two ways of saying the same thing, so no actual reason has been offered. Then, if "I am having thought X" needs a justification, we'd have to look elsewhere.

The problem I think you see is of your own creation. Or so it seems to me. — Banno

You may well be right. But I haven't yet satisfied myself one way or the other. Your input, as always, is appreciated.

That bird looks sad. Is he a cousin of the fly in the fly-bottle? (I also notice that he could leave the cage anytime he wanted to.)

it could have been better written. — javra

No worries, I'm not always a model of precision myself.

the proposition of “the planet is physical and roughly spherical” is taken to be an instance of knowledge, thereby being [a] JTB claim — javra

OK, good, so on this construal, JTB becomes a reasonable description of our ontic and epistemological requirements. We're not saying that "The planet is physical and roughly spherical" is known to be true, pre-JTB. Nothing is known to be true, in that non-fallibilist sense.* Rather, we bring our belief and our (presumably pretty impressive) justifications, and fill in the "T" with some such formula as you used above. The result is knowledge. This should make us suitably modest about what knowledge actually consists of, but at the same time extremely confident that the target statement is knowledge if anything is.

* The monkey wrench is logical and other putatively analytical truths. I think such statements require a different series, and type, of arguments to explain what knowledge of them would mean. Historically, was JTB proposed as being useful for determining that kind of knowledge? I'm used to thinking of it as an attempt to evaluate knowledge claims about the world, but I don't know the back-story. There's something odd about asking whether "If A, then not (~A)" is a belief, or how we might justify it. But I'll leave that for others.

You seem to be expecting something from the JTB account that it does not provide. It's not a theory of truth. — Banno

That's true (sorry!), but it's a theory of knowledge that includes, as one of its criteria, that a statement be true. So if JTB tells us that X is known, it must also tell us at the same time that X is true.

But see my response to @javra, below.

This is a very helpful analysis. It sharpens the question, Are we meant to take the knowledge guaranteed by JTB as infallible or certain (@Janus's question)? You argue convincingly that we can't -- that this can't be the point of JTB. So if we're happy to substitute "has no reason to suppose that one’s 'belief that X' is not in fact ontologically true" as a synonym for "knowledge", then all is well. I don't know whether every proponent of JTB would be happy with this, though.

To try to reduce possible confusion, how this works in practice: “I know that the planet is physical and roughly spherical,” is a claim of JTB. — javra

Here, I wonder whether you misstated your target sentence. Are you talking about a JTB claim for "The planet is physical and roughly spherical" or for "I know that the planet is physical and roughly spherical"? A great deal depends on this, so I'll wait until you reply before going on.

inside reasoning is non meta reasoning. And must be used to determine truth of an argument generally. Rather than using a meta lens like psychology or sociology or genetics.
— Jack2848

Yes, that's right. Typical 'outside' claims, of the type Nagel is criticising in that essay, are claims that attempt to justifiy reason based on evolutionary biology. — Wayfarer

And I would add that such claims help themselves to terms like "justify" or "explain" as part of their discourse about why reason can be reduced to biology! This would seem to be a performative contradiction, as Nagel says. Or else our entire understanding of what it means to justify or explain something has to change radically.

Q1a. Yes.
Q1b. Yes.
Q1c.Yes - follows from Q1a: if you believe it, you believe it to be true. — Banno

But Q1c was not about belief, but rather truth. Yes, it follows from believing something that I also believe it to be true, but that's not a reply to Q1c, which asks "Is it true?" Nothing I believe can supply the answer; it depends on the facts.

JTB is supposed to help us evaluate knowledge claims -- keep us epistemologically honest. And on this construal, it can't.
— J
It doesn't tell us if they are true or not, so much as if they are known or not. — Banno

That's what I don't see how to separate. We both agree that only true things can be known. So if JTB tells us that X is known, it must also tell us at the same time that X is true.

I'm good with all that. Just wanted to make the case that almost anything we claim to be true requires some (potential) justification.

If something is true by definition or if something is logically self-evident, or if the proposition concerns something being directly observed, then I would say we need no further justification. — Janus

I agree. But all three of these things -- truth by definition, logical self-evidence, and the reliability of direct observation -- are ways of demonstrating justification. To understand this, imagine explaining any one of them to an intelligent child. They all involve steps, cogitation, judgment, insight. We don't simply see why they are true, or at least not usually. In fact, as you know, the reliability of direct observation can be challenged, and the challenge is precisely for a justification as to how such observations lead to truth.

JTB sets out criteria for a sentence to count as knowledge. It is not a method for determining the truth of some sentence. — Banno

That's right. So, anticipating your investigator image, using JTB would go something like this:

Q1. Do I have knowledge of X (a proposition)? Depends on . . .
Q1a. Do I believe X?
Q1b. Can I justify my belief in X?
Q1c. Is X true?

Q1b is problematic, as we've noted, but let's allow that we understand what a "good enough justification" would look like. So we can go down the list:

Q1a. Yes.
Q1b. Yes.
Q1c. ????

What can we say about Q1c that doesn't involve an appeal to knowledge? We want to say, Yes, X is true. But we would have to know that, just as we know the first two answers, and we can't, because that begins the vicious circle.

I think what you're suggesting is that instead we should say, "I don't know if X is true. Such knowledge is impossible without circularity. But if it's true, then I know X. And if it isn't, then I don't." So, as you say, a strictly descriptive or criteriological formulation. However, I maintain that this is not only useless, but contrary to the spirit of JTB. JTB is supposed to help us evaluate knowledge claims -- keep us epistemologically honest. And on this construal, it can't.

That the sentence is true is one of the criteria for the sentence being known. This says nothing about how we determined if the sentence is true. — Banno

That's right. But then what should we use JTB for?

There is a difference between "P is true" and "J determined that P is true". JTB specifies that the sentence must be true, not that the sentence must be "determined to be true".

This seems to me to be the source of your confusion. — Banno

Well, I think it's JTB that's confused, not me. Because as I said to @Srap Tasmaner, what use is JTB if it can't show us how to tell whether we know something or not? Being told, "Well, you would know it, if it was true" is pretty thin gruel and, as I said, not to the purpose of JTB as I understand it.

You seem to have an image of an investigator looking at a sentence and saying "ok, Criteria one: I believe this sentence; criteria two: this sentence is justified by such-and-such; but criteria three: how can I decide if the sentence is true?" But that's not how the idea would be used - there's an obvious circularity in such a method, surely. If you believe the sentence (criteria one), then you already think it to be true and criteria three is irrelevant. — Banno

Good, this is a helpful image. And if we set it up like this, then it's another way of showing how JTB is faulty. Because it's absolutely right that the T criterion becomes irrelevant; that's what I've been arguing, using a different approach, all along. I would emphasize the justifications rather than the belief, but it comes to the same thing.

I think we can be skeptical any such theory is possible, either on general grounds of human fallibility or even on logical grounds (the problem of the criterion),

So what are we about? — Srap Tasmaner

Agreed. I'd be much more interested in a theory that could show how, in practice, we're able to make pretty good distinctions among degrees of likelihood, knowledge, certitude, etc. The case of analytic knowledge is perhaps special, but I won't open all that up in this context, since even a piece of analytic knowledge must have some justification.

I think JTB is intended as a test for knowledge, yes, not merely a description (to which no one has access!).

@Sam26 does seem to want to say, "My claim to know certain things is justified because I used a really good epistemology." I don't think it works that way. — Srap Tasmaner

Maybe not exactly, but I think Sam is nonetheless on the right track. We do know certain things, and we are justified in claiming we do, and without a really good epistemology (or epistemological practice), we'll make mistakes. I think a flexible JTB(+U) schema can help us understand how all this is possible. We just have to avoid some sort of essentialism or "definitionalism" (as @Banno has pointed out) about what counts as knowledge and justification. There are just too many uses, contexts, and practices.

That is, it suffices for the proposition to be true or false, whether there is any way to determine its truth value or not. — Srap Tasmaner

But that's the part I find incoherent. Is the idea that P need only be truth-apt in order for "P is a JTB" to represent knowledge? That can't be right. We need to know if it's actually true. So if we can't determine T in some way independent of J, how are we supposed to use JTB as a test for knowledge? What is the criterion that allows us to import "T" into the formula, if we can't know whether X is T?

If I justifiably believe that P, then if P is the case, I am in a state of knowledge that P, and if not then not. — Srap Tasmaner

Yes (leaving aside the earlier questions about "good justifications"). But if JTB can't help us tell the difference between being in a state of knowledge that P, and not being in that state, what good is it?

When do I ever know something is true apart from having the right justifications? — J

We know analytic statements are true. — Janus

But do we know this apart from the right justifications? I don't see how. Even something as clear as modus ponens can and must be explained and justified; we don't say "I just know it."

If we say, a person S knows that P when P is the case, they believe that P, and their belief that P is "justified," in whatever sense we give that word, then what S says or is entitled to say about their possible knowledge that P just doesn't enter into it — Srap Tasmaner

You're quite right. My use of "I can say" was loose talk, borrowed from a certain style of discussing these problems. More precisely: "what I can say" = "what I can think or believe to be correct or reasonable, and hence assertable in this sort of discourse." The actual saying or asserting isn't necessary, or even the point, as you show.

the difference between "P is true" and "I know that P is true".

These are not the same. — Banno

Right. As I wrote, above:

But JTB is not about what makes something true, but how I can say [see reply to Srap above] I know it to be true. The truth or falsity of the proposition under discussion remains what it is, no matter what I know or don't know. — J

But the T in JTB is dependent on P's being true, not on the circularity of your knowing that P is true.

Am I misunderstanding you in some way? You seem to miss this very obvious point. — Banno

Yes, I think we're a bit at cross-purposes here. The T in JTB is absolutely about something's being true. My question is about how we'd know it to be true. You seem to be saying that there's an independent way of determining whether X is true -- a pre-qualification, so to speak -- that will allow us to import the T into JTB, and then talk about our justifications. That's what I find confusing.

The entire question falls inside the scope of human activity, not ontology. Truth, as I know you firmly believe, is a property of propositions, not objects. If X is true, then X is a proposition. Yes, this proposition describes something else (fact, state of affairs, call it what you will), but that is a different matter. "The T in JTB is dependent on P's being true" -- yes, but if we don't ask "How can I know this?" then I don't understand how we'd ever be able to use T in JTB.

Having said all that, it's entirely possible that I've misunderstood you. :smile: So feel free to clarify.

A question remains though― what use is something's being true if we don't know it. — Janus

That's more or less what I'm wondering too, though I'd limit my wondering to the use of "true" in JTB.
I can conceive of other contexts for claiming that the concept of truth is useful, even if we don't know whether a given X is true.

Are you [@sime] saying that, a priori, we cannot know false propositions - that all the propositions we know are not false? — Banno

Yes, that's the right question, and returns us to the issues around JTB. JTB proposes that only true propositions can be known, AND that there is a way to determine truth apart from justifications. Crucial here is "determine truth," not "make X true." X will be true (or false) regardless of whether we can determine it to be so, but if we can't determine it to be so, how are we supposed to construct the T leg of JTB?

So maybe the “absolutely fantastic” fact isn’t that reason is supernatural intruding into nature, but that nature itself is fecund enough to give rise to symbolic beings whose grasp of universals is more than merely biological. — Wayfarer

Sure, works for me. I don't think we can insist on precision of language when talking at this level. We both are pointing to something quite extraordinary that seems to need explaining, or at least understanding.

The Koyré quote is interesting, though overly dire in my opinion. My take: Science often forces us to question where and how value and meaning arise, but rarely presents us with any reasons to doubt that they do; philosophers do that. So it's a good thing, a good challenge, for philosophy, to sharpen up our responses.

As is so often the case when I read broad statements about culture, like this one, I wonder who exactly is supposed to be believing and saying this stuff. I have several scientist friends and they certainly don't talk, or live, like this. Are these perhaps meant as unpalatable conclusions that scientists ought to draw, if they were consistent? A version of "What you're saying amounts to . . . "?

So now the task seems to be to 'explain' reason - this I take to be the task that the 'naturalisation of reason' has set itself. — Wayfarer

Yes. But as you point out, that's only one way to understand the explanatory task here. Nagel and sometimes Putnam want a different kind of explanation. I have little interest in naturalistic/evolutionary explanations of what reason is, but I very much want to know why it is, how it can be the case that the supernatural (non-pejoratively) arises within the natural. I believe this is the explanation of reason that Nagel also wants. Considered from a certain angle, there is something absolutely fantastic, or fantastical, about it -- how could such a fact have arisen?

Now on either construal of explanation, reason is indeed that which explains. And here, we want the rationale for reason itself. There is a sense, as Nagel shows, in which reason can explain itself: that's the "what" question. However . . . the worry is that any attempt to answer the "why" question is vacuous or incomplete. Is it explanatory to say, "The cosmos reflects an order and an intelligence" or "Human reason reflects the Logos" or to speak of "a natural place for reason in the grand scheme"? Mind you, I'm extremely sympathetic to these views, and I think they're probably close to the truth, but can we really say that they explain anything, as stated? Haven't we just provided a fancier description of what wants explaining? Or are they "a clue to the exit," the place where philosophy stops?

Have you read Logos, by Raymond Tallis? A good discussion of this issue.

PS -- offline till Monday . . .

The J in JTB is supposed to exclude cases of epistemic luck: the truth of your belief, if the belief was not formed in the right way, is not enough for us to count it as knowledge. — Srap Tasmaner

Yes. I took that to be understood. My question -- the "right question" part, I guess -- was what sort of answer a person would give if they were asked why X was true but also told, "You may not give your justifications." We feel there should be some answer to this, since after all it isn't our justifications that make a state of affairs true.

But JTB is not about what makes something true, but how I can say I know it to be true. The truth or falsity of the proposition under discussion remains what it is, no matter what I know or don't know. But my knowledge, according to JTB, depends on three things, two of which -- J and T -- seem viciously circular in this context, which again is epistemological, not substantive about the world. (And I raised, above, the question of whether even B can stand up, if I think I have a justification for something I don't actually understand: "If I believe something without fully understanding it, and I'm asked to give an account of what I say I believe, can I do it? Or would this reveal that the B of JTB in fact doesn't apply? - that I literally don't know what I believe." This connects with @Sam26's proposed criterion of "understanding.")

I think that all your very pertinent questions come down to versions of the same issue, which @Banno has also picked up on, namely whether the T in JTB is doing any useful work.

(I was asking) whether when you thought it was raining you would have said you knew it was raining. — Janus

Not if I was a proponent of JTB. Since, at that time, I had no way of knowing whether the "raining" statement was true apart from the cogency of my justifications, I would/should have said, "I believe I am justified in saying it's raining."

But this raises the deeper problem. When do I ever know something is true apart from having the right justifications? How can we make truth independent of justification -- make J and T genuinely separate criteria? Even the truth of analytic statements can be justified, indeed must be. Perhaps the idea is that some justifications cannot be insufficient or misguided. We can somehow know beforehand that there cannot be any defeaters.

And this connects with your questions about knowledge and certainty. I understand why JTB, taken rigorously, suggests that knowledge must be certain. Otherwise, how do we get "true" to do anything that "justified" isn't already doing? But if we decide to equate "true" with "certain," we get a possible answer.

The only issue with any of this is that it doesn't fit the way we actually think and talk about knowledge. I know the sun will rise tomorrow, in spite of being able to imagine defeaters. We'd have to say I didn't, on this view. Keeping J and T separate isn't worth paying this price, it seems to me.

The trail it sent me down was the implied ‘divinity of the rational soul’ in medieval philosophy (stemming from Aristotle’s ‘active intellect’.) — Wayfarer

Yes, that was certainly an attempt to explain how reason can be, and do, what it is and does. We're still trying to work out whether this is an explanation, or whether it uses language to explain away something we don't yet understand. And it's no help, as you point out, that this question is so often appropriated for a theological response.

Yes, that's eloquent. And again, what I respect so much about Nagel is that he isn't willing just to stop there. He still perceives a problem -- namely, how can it be the case that reason is this sort of thing, and that we humans are placed in the kind of relationship to it that produces "thought from the inside"?

Hence, It seems to me, ↪J's reservations. — Banno

Yes. Though maybe more in my post directly above that one.

But to be sure, at the core, we do not know things that are not true, we do not know things that we do not believe, and we ought be able to give an account as to why we know some proposal. — Banno

Right, there's something basically correct and useful about the JTB concept. I'd modify "an account as to why we know some proposal" to "an account as to why we believe or say we know some proposal."

What might be problematic here is some expectation that there be no exceptions, no fuzziness as to what counts as knowledge and what doesn't. — Banno

I've objected to the unclarity around justification vs. truth, but this is important too. As you say, we can just stipulate what "knowledge" will mean, and get on with it, but that's not very satisfying. The fuzziness around "knowledge" and "knowing" is what JTB tries to de-fuzz. If we agree that we can know things that aren't certain, then there may be room for degrees of knowledge as well. If the justification-truth circle is indeed a vicious one, as I suspect it may be, then we may have to settle for a less-than-perfect conception of what it means to know something,

Ideas can’t be explained in terms of something else, they are the fundamental coinage of rational thought. — Wayfarer

This idea is picked up in Thomas Nagel's The Last Word as well:

Whether one challenges the rational credentials of a particular judgment or of a whole realm of discourse, one has to rely at some level on judgments and methods of argument which one believes are not themselves subject to the same challenge. — The Last Word, 11

Nagel is honest and deep enough to also acknowledge:

Yet it is obscure how that is possible. Both the existence and the non-existence of reason present problems of intelligibility. — The Last Word, 11

So, as you say: THE key question of metaphysics. Nagel has done as good a job as anyone to make the case that reason is indeed "the last word."

it includes understanding (+U): You grasp the concepts involved and know how to apply them correctly, avoiding confusion in how words or ideas are used. — Sam26

Traditional JTB does not require fully grasping the ideas. I insist on it, so you demonstrate knowledge by using concepts properly. — Sam26

Just curious: If I believe something without fully understanding it, and I'm asked to give an account of what I say I believe, can I do it? Or would this reveal that the B of JTB in fact doesn't apply? - that I literally don't know what I believe.

the real issue lies in how we understand justification. — Sam26

Yes.

It is more than simply a person thinking they are justified. — Sam26

Yes.

when a defeater arises that overturns what seemed to be justified, we recognize that the claim was never knowledge to begin with, but only something that masqueraded as such. — Sam26

But doesn't this raise, again, the problem of the independence of justification from truth, and vice versa? If something can only be knowledge if it's true (along with J and B, and perhaps your U), what are the criteria for knowing when it is true, apart from those very justifications?

We have every (public and private) justification for believing the sky is blue (with all the usual qualifications about colors). If a defeater arose, such that we understood that the sky was not in fact blue, what has happened? You say, "The claim was never knowledge to begin with." But I say, "Yes, it was, on the JTB definition, because there was never an independent criterion for blueness apart from our justifications for believing the term applies to 'sky'. And that won't do, because we don't want an explanation of what knowledge is to leave room for that kind of error." This is a problem with JTB, not your very thorough argument that tries to rehabilitate it.

Here's another way to state the objection. How does a defeater work? It demonstrates that a previously held belief is untrue. How does it do this? By showing that the previously held justifications are inadequate to establish the truth of the belief. It can't talk about truth apart from the justifications. If we could know, or even think we know, truth apart from justifications, why would we need justifications to be part of knowledge? We could just "know the truth" and leave it at that.

In short, JTB is onto something important, but as formulated, it doesn't give us enough clarity about how truth and justification may be conceptually separated.

Returning to your 'raining' example, would you have said that you know it is raining? — Janus

Not if I accept JTB as the standard of knowledge. I can't say I know it's raining unless it's true that it's raining; truth is the third leg of the tripod. What complicates this is the justification part: Am I justified in saying "It's raining" even if I don't know it to be true? I'm not sure we have rules for this, or clear intuitions about what we would feel in every case. A slippery concept, as you say. In this case, I'd probably say "I believe it's raining" or "I think it's highly likely it's raining." But if you then asked me, "Is your belief justified?" the answer isn't obvious. I might say, "Yes, up to a point" or "I have good reasons." The crux is that, following @Sam26's thought, there needs to be some space between justification and truth in order for JTB to really be a three-legged tripod. I have to be able to be justified yet wrong.

would it not be the case that sometimes we possess knowledge, but cannot know that we do? And doesn't that seem a little weird, that we might know something to be the case, but not know that we know? — Janus

A good question. Again accepting JTB, the answer has to be no, unless you're wanting to tweak how we understand "possess." If I don't know whether [consciously possess the knowledge that] X is true, then I can't claim to know X, according to JTB. It might turn out that "I knew it all along," but this is only a semi-serious use of "know," I believe. If Joe is revealed as the killer in a mystery movie, and someone says "I knew it all along" but during the film was guessing with the rest of us, we don't take the claim to knowledge very seriously.

Assuming that we can say that some beliefs are justified, which might yet turn out to be wrong . . . — Janus

This is the same problem as above, I think. What counts as "justified" is slippery. Also, your phrasing is a little ambiguous: Do you mean "turn out to be wrong that what we believed was justified" or "turn out to be wrong that what we named as a justification was incorrect"?

EDIT: Sorry, the last phrase should be "turn out to be wrong that what we named as a justification was correct."

But, consider Descartes' comment here:

“But when I perceive something very clearly and distinctly, I cannot but assent to it. Even if I will to the contrary, I am nevertheless drawn into assent by the great light in the intellect; and in this consists the greatest and most evident mark of human error.” — Hanover

This is a significant example of the kind of thing I'm concerned about. Is "being drawn into assent" being caused to assent? Or is it better described as having a reason to assent? Is "I assent to X" a distinct thought from "I perceive X clearly and distinctly"? There are several other m2m questions I want to address, but this is right on. So is the question of control over ones thoughts.

And thanks for the SEP reference.

The problem is more that math seems "un-inventable" -- that is, its truths appear necessary, not something we could have chosen. I agree that questions about "relative reality" are largely terminological -- but questions about the differences between, say, the number 12 and a rock are not.

Platonism, as mathematician Brian Davies has put it, “has more in common with mystical religions than it does with modern science.” — What is Math? Smithsonian Magazine

I suppose. But this is a little hard on modern science. "Tough-minded" empiricism, perhaps, has trouble with abstracta. But scientists commonly work with laws and math, neither of which can be perceived or measured. I agree that some scientists don't appear to see the contradiction between that and nonetheless denying any reality to non-space-time items.

But the same can be said of the real numbers, generally. Do they exist prior to being discovered? — Wayfarer

Yes. I picked a number no one knows just to make the point clearer. And your "real/exist" schema works well to help keep things straight.

it is not referring to a domain in the sense of a place. — Wayfarer

Do some people think it is? A "place" without space and time? Hmm . . .

It is the domain of ideas that can only be grasped by a rational intelligence. But at least some of these are not generated or created but discovered by the mind. I think that's what Popper was driving at. — Wayfarer

Popper did think we created them. He didn't believe World 3 objects exist apart from being created by World 2 thoughts. I'm more inclined toward your idea, which is closer to (non-naive) Platonism. But then you do require the intellectual act itself in order to bring such an object into reality, so perhaps this is closer to Popper after all.

I don't see why a N-teenth prime is a problem. We know how mathematics works, whether we discovered it or invented it. — Patterner

Sure. It's only a problem if you're philosophically bothered by the question "discovered or invented?"

But just to be clear about this . . . I do think that Popper's World 3, which refers to abstracta in general, apart from any particular physical/mental instantiation (Worlds 1 and 2), has to be understood as independent. We're still seeking good explanations of exactly what that means -- how it can be the case that there is a N-teenth prime even if no one knows what it is, or has ever had the thought of it.

we can experiment on the physical world and come up with causal explanations in a way that we can't do with the "non physical mental world" you suppose exists. — flannel jesus

I think (non-behaviorist) psychologists would be surprised to hear this! And just to be clear, I doubt whether there's a "mental world" that exists apart from physical supervenience. The whole "worlds" metaphor gets a good discussion in Popper's Objective Knowledge.

But you're right that my question overlaps with the concerns of psychology.

It didn't seem as if the other "m2m" thread was going in the direction that interests me, so I haven't read it carefully.

I think the paucity of literature on m2m is for a different reason. The general assumption is that causal language ought to be reserved for interactions that have at least one physical component -- that is, physical-to-physical (p2p), physical-to-mental (p2m), or mental-to-physical (m2p). On this understanding, mental events can't cause other mental events. I'll have a lot more to say about this, if I ever get the darn OP written. But quickly: We can, and do, say that propositions provide reasons for holding other propositions -- but this is supposed to take place in the mysterious world where propositions exist and interact without any minds to think them. And/or, we can say that a thought -- understood now as a mental event and not a proposition -- associates with another thought. I find this also mysterious, or at any rate a mere sketch. But the idea is that any talk of causality can only be brought in if the mental is tied to a physical substrate of some sort. And of course it presupposes a mechanistic view of causality.

These might sound like vague poetic gestures but in reality they're often vivid and life-changing realisations — Wayfarer

Absolutely. The "birth and death" imagery is constant across cultures, for good reason.

. . . apodictic, even, to those who undergo them. — Wayfarer

I know it seems that way. But we have to beware of such claims. There are too many instances of people who've been visited by powerful realizations of one sort or another, and then draw mad conclusions about the meaning of it. What's apodictic, arguably, is the the power and the reality of the experience. I don't think its source and interpretation can be similarly self-verifying.

If I can only determine some fact on my own can I talk about it being objective? — Janus

I think so. The key phrasing is "can be verified," not has been. The bird in the tree was in principle verifiable by anyone looking; your thought of X isn't. That, at any rate, is the difference I'm suggesting is useful. It may not correspond to exactly how you, or everyone, thinks about the terms "objective" and "fact." For instance, you may prefer to reserve "objective" for something that not only can be, but has been affirmed by others.

The ambiguity here is the reason I prefer 'intersubjective' to 'objective'. The witnessing of the alighting bird and the falling leaf could in principle be shared. An experience of God, or the thought I am having right now cannot be, even in principle. — Janus

Yes. "Intersubjective" works perfectly well to express the difference. As you probably know by now, I'm not a fan of arguing overmuch about which terms to use, as long as the users understand each other. What counts is the difference, not the labels for it.

I don't count introspection as all that reliable. — Janus

Really? We know the familiar puzzles and loopholes about introspection -- but by and large? I rarely find myself wondering if I am indeed having the mental experience I take myself to be having. Is that too trusting, do you think? It seems to have proved reliable. Now, if you bring in unconscious or subconscious mental influences -- yes, that's different. But here, we're not questioning an experience per se ("I am thinking of X") so much as the motives or meanings that may lie behind the experience ("Yes, but why am I thinking of X? Does my thought of X really mean what I believe it means?"). The thought of X remains a given.

Many folk seem to be uncomfortable with uncertainty...but for me understanding uncertainty and the challenge of living with it is a major part of doing philosophy. — Janus

Agreed, and we could expand that to say, "Doing philosophy helps us understand what we even mean by words like 'knowledge' or 'certainty', words which seem to promise a great deal when used loosely, but which under scrutiny often don't cash out." Provisionally accepting and rejecting is how we get our beliefs to fit with our lives, it seems to me. To ask for more may be unreasonable, except on a few core issues.

This seems to be the central issue―what is a fact, and does the qualifier "objective" add anything? — Janus

One helpful way of using the terms might be: an objective fact is one which others can verify, whereas "I'm having thought X at the moment" is a fact, but not objective.

Facts are usually taken to be determinable by either observation or logic. — Janus

As above, the question is, Whose observation? I'm assuming you don't think we need objective confirmation of observations about what goes on in our minds (as a rule).

how will you know, any more than you would in this life, that an experience that you felt was of God is really a confirmation of said entity? — Janus

Yeah, the more I think about Hick's idea, the less I like it. I suppose what he meant was, If you had an experience after death that checked all the boxes of what mystics claim God (and the afterlife) is like, and you in fact found yourself surviving death, as promised, you'd probably be convinced! But we're guessing about how reliable afterlife experiences are . . .

I continue to think that a lot of this comes down to the level of confirmation required before one is willing to claim knowledge of something. We know that different experiences and facts have different criteria. Do I know my head hurts in the same way I know the solution of an equation? No, but surely both are types of knowledge. With a mystical experience, what criteria do we need (using "mystical experience" to mean a genuine one, one that really is of a god or cosmic consciousness)? As long as we agree that some criteria must apply, then the door is open for reasonable dialogue. What we want to avoid is either a) "My experience is self-verifying; I couldn't be wrong" or b) "Since we know there are no gods, your experience can't be genuine; no conceivable criteria could suffice."

Thanks, on my list.

the Aristotelian sense of logos as both reason and structure — Wayfarer

Everything you wrote about Hart and Vervaeke is fascinating and on point for me (though I don't see Hume as the diabolus ex machina they do). My particular m2m problem is a bit different, but can hardly be addressed without taking account of the perspectives you're describing.

I was especially struck by the quoted phrase. I've long held out for a difference between causes and reasons. If we can speak meaningfully about m2m causation, then I think causation has to be understood, or interpreted, as a type of reason, not a physical cause. And the logos concept has a lot to offer here. How can a mere structure also provide reasons that cause/influence/lead to mental events? And yet, when we entertain a syllogism, isn't this what happens? But the problem begins even before thought is seen as syllogistic: Somehow, what we call the "content" of a thought (be it propositional or imagistic) appears to provide causes (or reasons) for other thoughts. A reductively psychological explanation involving "associations" will not suffice, as I hope to argue.

Thanks, but what are you quoting?

It depends on the stance. Substance dualists have a completely different view to monists. — I like sushi

Sure. I don't want to get ahead of myself, as I'm still drafting the OP, but one of the difficult issues is that you need to first lay out some plausible positions on how the mental relates to the physical, before you can then posit solutions for how to understand (alleged) mental-to-mental causation.

The other big issue, which has already come up in some of the responses to this query, is that words like "mental" and "thought" can be taken from the point of view of logicism, or of psychologism. We do both, in our ordinary talk, so it's easy to accidentally confute them. I think Frege was right in wanting to keep them strictly separate. I'll have more to say about that. But could the concept of causation figure in either construal? We don't usually talk about the premises of a syllogism causing the conclusion, whereas the much weaker link of "association" (a very unfortunate term, but we seem to be stuck with it) does carry some causal weight, at least in common parlance, because we imagine this happening in a particular mind, not in Proposition World.

Anyway, to be continued, and thanks for everyone's interest and help -- even those of you who think m2m causation is impossible!