The point of my paper (the paper this thread is based on) was to strengthen traditional JTB with Witt's later philosophy.

Thanks, this is very good. You've helped me understand better what's at stake in the particular, problematic "why?" When this level of "why?" is reached, the question is actually no longer about the original subject (in this case, having two hands). It morphs into a demand for justification of the entire conceptual apparatus. And since this must inevitably include the concept of "justification" itself ("borrowing the tool") . . . we have a problem.

The only place I'd put up a little flag would be when you speak about "the ordinary criteria as illegitimate in advance" as a sign of hinge-questioning doubt. This problem goes back to Descartes, and is outside the scope of your OP, but I would make the case that Cartesian methodical doubt doesn't actually posit anything as illegitimate in advance, and neither does the skeptic in our example. In both instances, the skeptic is really raising a question about certainty, not about some subject. No genuine doubt is being expressed -- existential doubt, I might call it -- concerning two-handedness. Doubt is wielded as a tool to sculpt certainty, to learn how far the whole method can be pushed before we have to cry "I can conceive of no further doubt!"

The only place I'd put up a little flag would be when you speak about "the ordinary criteria as illegitimate in advance" as a sign of hinge-questioning doubt. This problem goes back to Descartes, and is outside the scope of your OP, but I would make the case that Cartesian methodical doubt doesn't actually posit anything as illegitimate in advance, and neither does the skeptic in our example. In both instances, the skeptic is really raising a question about certainty, not about some subject. No genuine doubt is being expressed -- existential doubt, I might call it -- concerning two-handedness. Doubt is wielded as a tool to sculpt certainty, to learn how far the whole method can be pushed before we have to cry "I can conceive of no further doubt!" — J

From a Wittgensteinian standpoint, I still can’t make sense of the Cartesian maneuver as doubt. Doubt isn’t a free-floating posture you can apply to anything at will. It’s a move inside a practice, and it only makes sense where there are criteria for what would count as checking it, correcting it, or settling it. When you try to doubt everything at once, you don’t get a deeper form of doubt, you remove the background that gives “doubt,” “test,” and “justification” their role in the first place.

That’s also why it helps to keep my four senses of certainty explicit: subjective certainty (conviction), hinge certainty (what stands fast and makes inquiry possible), epistemic certainty (defeater-resistant stability in practice), and absolute certainty (logical or moral necessity). Ordinary, practice-governed justification aims at epistemic certainty. Cartesian doubt pushes toward absolute certainty, and it treats hinge certainties as if they were ordinary claims waiting for ordinary support. From the Wittgensteinian angle, that isn’t a legitimate extension of doubt, it’s a shift in the grammar of the activity.

The issue isn’t that the skeptic declares ordinary criteria illegitimate. The issue is that the exercise changes the kind of question being asked, and once it does that, it stops looking like genuine doubt within a practice and starts looking like a philosophical performance aimed at an impossible standard.

The “magically turns into not knowledge” worry comes from treating knowledge as if it had to be indefeasible. — Sam26

Which is exactly what JTB does. I understand you’re trying to modify it to address that issue, but I’d rather just toss the whole thing in the hopper.

We say, “I knew, given what I had,” and we also say, “I was wrong.” Those aren’t contradictions. They mark two different evaluations: what was justified at the time, and what we now know after a defeater has arrived. — Sam26

Those are fine things to say. So why do we need all the JTB trappings—with or without U. What I want to do is focus on the important part of the JTB formula—J. Adequate justification is what’s needed. It’s the best we can do. What does adequate mean? It depends mostly on the consequences of being wrong.

That's also why my guardrails matter. They're not demanding absolute certainty. They're making explicit the constraints we already use to separate knowledge from lucky success and from fragile support. Defeater screening, in particular, is not a demand to foresee every possible
counterexample. It's the ordinary discipline of not ignoring live alternatives and known failure modes. — Sam26

You talk about this with really different language than I do. That’s why I stopped participating in this discussion. As I said, I don’t want to try to make JTB work, I want to discard it entirely.

If you keep “adequate justification,” you haven’t really escaped JTB, you’ve just renamed it, and you’ve made key distinctions harder to state.

“Adequate justification” still presupposes a target. Adequate for action isn’t the same as adequate for knowledge. If you collapse knowledge into “what I’m willing to act on,” you turn epistemic standing into risk tolerance. Two people with the same evidence can differ just because they’re more cautious. That’s prudence, not knowledge.

The so called JTB trappings are the distinctions you still need. Truth is about how things are, belief is what the subject holds, justification is the belief’s standing. If you throw those out, you end up rebuilding them anyway to explain the difference between “I acted responsibly” and “I knew.”

Your engineering language already matches my guardrails. QA/QC is No False Grounds. Standards of practice are Practice Safety. “Don’t ignore known failure modes” is Defeater Screening. The real question isn’t JTB versus adequacy. It’s whether “adequate” stays vague, or whether you spell out the failure modes that make a belief look supported when it isn’t.

Discarding JTB doesn’t remove Gettier, it relocates it. If knowledge is “adequately justified true belief,” you still need to exclude lucky truths. Either you tighten adequacy to rule out luck, which is exactly what Practice Safety and defeater sensitivity do, or you let luck count as knowledge.

If you keep “adequate justification,” you haven’t really escaped JTB, you’ve just renamed it, and you’ve made key distinctions harder to state. — Sam26

No. It’s adequately justified belief. Truth isn’t in the equation.

Adequate justification” still presupposes a target. Adequate for action isn’t the same as adequate for knowledge. — Sam26

As I define it, adequate justification means sufficient to allow responsible decision making. So, yes. Adequate for action is the same as adequate for knowledge.

The real question isn’t JTB versus adequacy. It’s whether “adequate” stays vague, or whether you spell out the failure modes that make a belief look supported when it isn’t. — Sam26

You can make the standards for adequacy anything you want. It’s a question of risk management and liability.

Discarding JTB doesn’t remove Gettier, it relocates it. — Sam26

As I quipped previously, let’s not get into Gettier. I have strong negative feelings about the whole subject.

That said, I lean more toward the first analysis than the second. Is it possible to doubt whether I have two hands? Yes. Do we know the general sorts of things that justify our (comparative) certainty about two-handedness? Yes. — J

My analysis would actually be closer to the second than the first, and I largely agree with 's reply, though I framed it differently. The basic idea is that some "why?" questions misfire because they try to put into question that which makes questioning possible in the first place. Framed like this, it can be seen as a retorsion argument, or argument from pragmatic contradiction.

The basic idea is that some "why?" questions misfire because they try to put into question that which makes questioning possible in the first place. Framed like this, it can be seen as a retorsion argument, or argument from pragmatic contradiction. — Esse Quam Videri

Yes, I think we're all on the same page with this now. I raised a question about how the Cartesian method does or doesn't fit this conception, and that could be a good discussion too (I appreciate what @Sam26 is saying about it) but outside the OP.

Doubt isn’t a free-floating posture you can apply to anything at will. It’s a move inside a practice, and it only makes sense where there are criteria for what would count as checking it, correcting it, or settling it. — Sam26

Right, that would be the difference between a skepticism that is meaningful, versus one that merely capitalizes on our language's ability to frame "why?" questions. As above, I think Descartes stays within a recognizable practice using his method, but TBC elsewhere.

Back to Sam's questions:

Do you think Gettier cases still refute JTB even if we build in the guardrails and the “+U” clarification.

Is my diagnosis too dependent on relabeling the justification condition rather than answering the core intuition. — Sam26

Your analysis of JTB pretty well answers the first question, I think. You conclude, "Gettier is trading on an impoverished picture of justification," implying that Gettier cases never refuted JTB, properly understood, in the first place. Your guardrails and "+U" show why, and once again it's key to your concept that it is a showing, an explanation, not an added ingredient required to save JTB from the jaws of Gettier.

The second question is a little unclear to me. How would you lay out "the core intuition"?

You’re right that my view is that Gettier trades on an impoverished picture of justification, and that the guardrails and the “+U” are meant to show what our practice already treats as decisive, not to bolt on a fourth condition. I find it amazing that people find Gettier significant.

On your second question, by “the core intuition” I mean the feeling that makes Gettier cases grip us:

The belief is true.

The subject can qbite supporting considerations that look like justification.

Yet the truth shows up by luck, because the support is fragile, or dependent on a false ground, or insulated from the mistake-conditions the practice recognizes.

That’s why we resist calling it knowledge, even though it can look like JTB is met on the surface.

This is not rare. It happens a lot in ordinary life because most of what we call knowledge isn’t absolute certainty. We’re usually dealing with epistemic certainty, defeater-resistant stability in practice, and in many domains that stability is unavoidably probabilistic.

My diagnosis isn’t just relabeling. It’s an attempt to explain why the Gettier intuition arises so often: we mistake surface marks of support for justificatory standing. Once you make explicit the ordinary constraints that already govern standing, No False Grounds, Practice Safety, and Defeater Screening, the Gettier case stops looking like a refutation of JTB and starts looking like a case where the belief was true, but the route was lucky or too fragile to count as knowledge.

My analysis would actually be closer to the second than the first, and I largely agree with ↪Sam26's reply, though I framed it differently. The basic idea is that some "why?" questions misfire because they try to put into question that which makes questioning possible in the first place. Framed like this, it can be seen as a retorsion argument, or argument from pragmatic contradiction. — Esse Quam Videri

I agree. Some “why?” questions misfire because they try to question what makes questioning possible in the first place. In that sense the move is retorsion, a pragmatic contradiction: it borrows the norms of justification while attempting to place the background that makes those norms operative on trial. The key is to keep the point limited to that kind of global “why?,” and not treat it as a dismissal of ordinary, practice-governed activiity for reasons aimed at epistemic certainty.

Many people treat Cartesian doubt as if it were the gold standard of intellectual seriousness. From a Wittgensteinian standpoint, I don’t think it works that way, because it misunderstands what doubt is, and what counts as a legitimate doubt.

Doubting cannot be applied in any context; it's a move inside a practice. It has a role only where there are standards for what would count as checking it, correcting it, or settling it (this is an important point). If I doubt whether the train is at 9, I know what would settle it: look at the schedule, check the platform, ask an attendant, and so on. That doubt makes sense because the practice contains criteria that can settle the matter.

Now consider the Cartesian project of doubting everything. When doubt is applied universally, it stops working as doubt, because it starts targeting what I call hinge certainties, the background that makes the entire practice of questioning and checking possible. Hinges are not conclusions we reached by evidence. They are what stands fast in our activity: the things we take for granted when we test, correct, infer, and even when we doubt. If you try to put that background on trial using the very tools that depend on it, you haven’t discovered a deeper form of doubt. You’ve changed the grammar of what it means to doubt.

This is where my four uses of certainty help keep the discussion honest:

Subjective certainty: conviction, how settled something feels.

Hinge certainty: bedrock, what stands fast and makes inquiry possible.

Epistemic certainty: defeater-resistant stability in practice, enough for responsible action.

Absolute certainty: logical or moral necessity.

Ordinary justification aims at epistemic certainty, not absolute certainty. It’s corrigible and defeasible, but it’s still knowledge in the ordinary sense. Cartesian doubt quietly shifts the goal toward absolute certainty, and then it treats hinge certainty as if it were a hypothesis that ought to be justified in the same way as an ordinary claim. That’s the mistake.

The Wittgensteinian objection isn’t “Descartes is being irrational.” It’s that the method asks for the wrong kind of thing. It demands that the framework be justified by the very methods the framework makes possible. That’s why the Cartesian maneuver often feels impressive but doesn’t actually describe how doubt and justification function in real epistemic life.

If someone insists Cartesian doubt is legitimate, the pressure question is simple: what would count as settling the global doubt. If the answer is “nothing could,” then the exercise isn’t an epistemic demand inside a practice. It’s a philosophical performance aimed at an impossible standard. And once we see that, we can stop letting it redefine what “justification” and “knowledge” mean in ordinary practice.

AI and why it matters to my paper

A quick application that’s relevant to why I wrote this paper at all. One reason I keep talking about “justificatory standing” and “understanding” is that we now live in an environment where it’s easy to generate what seems like justification. AI is the clearest example.

In my paper, I’m not saying AI can’t output true statements, or that it can’t be useful. It can. My point is narrower: producing fluent answers, even with citations, isn’t the same thing as knowing. Knowledge, as I’m using the term, involves a belief’s standing inside a practice, answerability to error, correction, and defeaters. A model can mimic the surface marks of that standing (Searle makes similar arguments), it can sound like it understands, it can even be right, but it doesn’t occupy the practice in the way that makes it responsible for tracking mistake-conditions, handling defeaters, and revising under correction.

This is exactly why I added the “+U” clarification. Understanding, on my view, isn’t a fourth ingredient. It’s the competence to track what would count against a claim, what would defeat it, and what correction would look like. AI can help us do that work, but it can also tempt us to skip it by handing us ready-made conclusions that look justified.

For me, the AI case isn’t a side issue. It’s a modern stress test: it shows how easy it is to confuse “looks justified” with “has justificatory standing,” and that confusion is the same pressure point that Gettier cases expose in a more controlled form.

I appreciate these thoughts on the Cartesian method. Possibly I'm not quite seeing your point, because my defense of Descartes would be simply this: There is no global doubt. He doesn't doubt everything, he does reach an endpoint, and it is absolutely certain, at least to him. If he had gone on to doubt the cogito, your analysis would be correct, and Descartes would be the first to agree -- doubting the self is doubting the entire framework for doubt.

As to whether the method occurs within a practice, I think it does: Descartes is clear about what would dispel or legitimize a given doubt. Granted, there is debate about whether his criterion (which rests on a particular notion of incorrigibility) is a good one. But we have to remember that Descartes's target is doubt and certainty themselves, not whether a certain subject "really" is how it seems. As he wrote, "No one of serious mind ever doubted" the existence of the external world.

You say, "Ordinary justification aims at epistemic certainty, not absolute certainty," and perhaps this is key. The Method is not ordinary; it doesn't attempt to mimic how we arrive at epistemic certainty. Descartes's project was weirder than that.

I find it amazing that people find Gettier significant. — Sam26

Yeah, and that's why I was curious what you thought the "core intuition" was. Perhaps it was deeper than I'd thought . . . but no, I'm with you on this.

*
I'd meant to circle back to this:

You/we take it to be certain that the role of understanding in human consciousness is significant, that it makes a difference, that it is a desideratum quite separate from knowledge — J

I think you’re close.

I’d just tighten the hinge, so it isn’t framed as a claim about human consciousness, as if it were an empirical thesis. In my use, the hinge is more grammatical than psychological: — Sam26

Could you say more about this? I think I see why you believe that talk of consciousness in this context has to be empirical, but before replying I want to be sure I understand you.

Thanks, that helps me understand what you’re defending in Descartes, and I’ll grant two points up front. First, Descartes isn’t doing “global doubt” in the crude sense of doubting absolutely everything forever. Second, his project is weirder than ordinary life, he’s trying to sculpt certainty itself, not simply settle ordinary questions.

Even so, my Wittgensteinian worry doesn’t depend on caricaturing him as a fool who doubts everything indiscriminately. The worry is about the kind of standard he builds into his method. When the method’s endpoint is absolute certainty (indubitability), and when the method treats the ordinary grounds of our practice as always defeasible in principle, it stops functioning as doubt in the ordinary, practice-governed sense. It becomes a philosophical performance with an atypical success condition: certainty that can’t be unsettled by any defeater the practice would normally recognize. That’s not an accusation, it’s a diagnosis of what the method is doing.

This is exactly where my certainty distinctions matter. Ordinary justification aims at epistemic certainty, defeater-resistant stability in practice. Descartes is aiming at absolute certainty, and the danger is that people let that aim quietly redefine what counts as justification and knowledge in ordinary epistemic life. My project in the paper is explicitly not that. I’m trying to make practice-governed justification explicit, including error, correction, and defeaters, without importing an absolute-standard demand that collapses most knowledge into “not really knowledge.”

On Gettier, I’m with you that the literature can become inflated. In my paper I’m not treating Gettier as an existential crisis for knowledge. I’m treating it as a diagnostic that exposes a common confusion: the slide from “looks supported” to “has justificatory standing.” That slide shows up constantly in real life, and it’s even more visible now in environments where the appearance of justification seems like justification.

Now to your final question about the hinge I tightened. When I say the hinge is “more grammatical than psychological,” I mean this. I’m not asserting an empirical thesis about consciousness, as if I were claiming “understanding has causal power in the brain” or “understanding is a measurable mental property.” I’m pointing to the role the concept plays in our justificatory practices. We already treat it as a real difference between (a) repeating conclusions and (b) being able to track mistake-conditions, defeaters, and correction. That difference shows up in how we assess competence, explanation, and responsibility in reasoning. In that sense it’s grammatical: it’s built into how “justification,” “mistake,” “correction,” and “understanding” function in our practices, regardless of any particular theory of consciousness.

The hinge isn’t “consciousness has this property.” The hinge is that the distinction between genuine grasp and mere repetition is constitutive of what we mean by justificatory standing. That’s the sense in which skepticism about understanding can become self-undermining: it tries to erase a distinction the practice relies on to make justification intelligible.

Just to emphasize: Descartes isn’t just doubting particular claims, he’s trying to doubt the very structure that makes doubt intelligible, and that’s why, from a Wittgensteinian standpoint, the method misfires as doubt.

That would be the point in question. Bernard Williams, in his book on Descartes, has this analysis:

When we reach the fully 'hyperbolical' doubt, as Descartes called it, we encounter a new kind of problem, which concerns the meaning of the proposition which the Doubt invites us to entertain. What is the content of the idea that, compatibly with other things seeming as they do, there might not be a physical world at all? If the hyperbolical doubt were arrived at merely by generalization from the particular doubts . . . it does not look as though there could be a coherent answer to this question. All the cases of error which the Doubt seized on in the earlier stages of the argument involved the use of some perceptions to correct others, and while we might be able to say, consistently with that, that we were not absolutely sure at any given moment that the present perception was veridical, we could not consistently say that no perceptions were. — Williams, Descartes: The project of pure enquiry, 57

Would you agree that this is the Wittgensteinian objection? If so, I can go on to say more about how Williams defends Descartes here.

I’m not asserting an empirical thesis about consciousness, as if I were claiming “understanding has causal power in the brain” or “understanding is a measurable mental property.” I’m pointing to the role the concept plays in our justificatory practices. — Sam26

Yes. But isn't it also the case that understanding is an actual mental phenomenon, something that can occur for you or me? Or perhaps this represents a philosophical difference along the usual public/private lines; perhaps you don't countenance talk of inner mental states, etc. I do, but I'm happy to acknowledge that your project doesn't need a decision one way or the other about that in order to discuss how justificatory practices work.

hat would be the point in question. Bernard Williams, in his book on Descartes, has this analysis:

When we reach the fully 'hyperbolical' doubt, as Descartes called it, we encounter a new kind of problem, which concerns the meaning of the proposition which the Doubt invites us to entertain. What is the content of the idea that, compatibly with other things seeming as they do, there might not be a physical world at all? If the hyperbolical doubt were arrived at merely by generalization from the particular doubts . . . it does not look as though there could be a coherent answer to this question. All the cases of error which the Doubt seized on in the earlier stages of the argument involved the use of some perceptions to correct others, and while we might be able to say, consistently with that, that we were not absolutely sure at any given moment that the present perception was veridical, we could not consistently say that no perceptions were.
— Williams, Descartes: The project of pure enquiry, 57

Would you agree that this is the Wittgensteinian objection? If so, I can go on to say more about how Williams defends Descartes here.

I’m not asserting an empirical thesis about consciousness, as if I were claiming “understanding has causal power in the brain” or “understanding is a measurable mental property.” I’m pointing to the role the concept plays in our justificatory practices.
— Sam26

Yes. But isn't it also the case that understanding is an actual mental phenomenon, something that can occur for you or me? Or perhaps this represents a philosophical difference along the usual public/private lines; perhaps you don't countenance talk of inner mental states, etc. I do, but I'm happy to acknowledge that your project doesn't need a decision one way or the other about that in order to discuss how justificatory practices work. — J

Yes, I’m basically with Williams there, and I do think what he’s pointing to lines up with the Wittgensteinian point. Once doubt becomes “hyperbolical,” it stops looking like an extension of ordinary doubt and starts raising a question about whether the doubt still has content. The earlier stages of doubt trade on the practice of using some perceptions to correct others, but the global move, “no perceptions are veridical,” threatens to remove the very contrast class that makes “veridical” and “error” intelligible. That’s very close to what I mean when I say the Cartesian maneuver starts to doubt the structure doubt depends on.

So yes, I’d say Williams is articulating a Wittgensteinian style objection: hyperbolical doubt risks misfiring because it tries to generalize beyond the conditions under which doubt and correction have a role. If you want to explain how Williams defends Descartes, I’m interested, but I’d also want to keep the distinction clear between (a) Descartes as a philosophical exercise and (b) whether that exercise should be allowed to set the standards for ordinary, practice-governed justification aimed at epistemic certainty.

On understanding as a mental phenomenon: I’m happy to grant that understanding can be an inner occurrence, something that happens to you or me. I’m not denying inner life. My point is only that my argument doesn’t hinge on a metaphysics of mental states. What matters for my project is that “understanding” marks a real difference in our epistemic practices: the difference between repeating conclusions and being able to track mistake-conditions, defeaters, and correction. That’s the sense in which I called it grammatical rather than psychological. It’s about the role the concept plays in how we assess justifiable conclusion, even if there’s an inner phenomenology of grasping.

I don’t need to take a hard line on public versus private. I can accept inner understanding as real, while still insisting that justificatory standing isn’t a private feeling and can’t be reduced to a report of how things seem. The practice-governed side is what I’m trying to keep in view.

I will be posting my paper in pieces for those who want to read it. I'll number the posts.

Post #1

Justified True Belief Plus Understanding: A Wittgensteinian Extension
Samuel L. Naccarato

Abstract

This paper reexamines the classical model of knowledge as Justified True Belief (JTB) and argues that its core insight is clarified, not replaced, by making explicit what our justificatory practices already presuppose. Drawing on Wittgenstein’s later philosophy, especially his discussions of language-games, grammar, and hinge propositions, I argue that justification does not operate in isolation. It functions within shared forms of life and rests on a background of bedrock certainties that stand fast for us and make doubt and inquiry possible. These certainties are foundational in a non-epistemic sense. They are not themselves justified; they make justification possible.

Truth remains the success condition for knowledge. To say that a belief is true is to say that the world is as the proposition represents it. In this framework, understanding is not an additional requirement placed alongside truth, belief, and justification. It is internal to justification, the conceptual competence by which a belief achieves its proper standing within an epistemic practice. This is why Gettier-style cases lose their force. They depend on a misleading picture of justification and on beliefs that only appear to possess the right standing.

To make this structure practically applicable, I introduce three guardrails that discipline justification, No False Grounds, Practice Safety, and Defeater Screening, and I distinguish five non-hierarchical routes through which justification typically proceeds: Testimony, Logic, Sensory Experience, Linguistic Training, and Pure Logic, understood in its boundary-setting role. The result is an account of knowledge that preserves realism without dogmatism and clarifies how justification functions in ordinary epistemic life, including under the pressures introduced by contemporary information systems and artificial intelligence.

If you want to explain how Williams defends Descartes, I’m interested, but I’d also want to keep the distinction clear between (a) Descartes as a philosophical exercise and (b) whether that exercise should be allowed to set the standards for ordinary, practice-governed justification aimed at epistemic certainty. — Sam26

Yes, that distinction is important, and as we've said, Descartes's project is off on a tangent from ordinary epistemic certainty. His kind of certainty is interesting to analyze, but no one would reach for Cartesian doubt as a way to understand JTB. Here's how Williams puts it:

There is no question, we must always remember, of hyperbolical doubt playing any rational role within ordinary life: the Doubt is to be taken entirely seriously in the context of an enquiry into what can most certainly be known to us . . . but [as Descartes says] 'one must bear in mind that distinction, which I have insisted on in various places, between the actions of life and the search for truth . . .'" — Williams, 61

This is precisely the same distinction you want to make, I believe -- except that for you, "the search for truth" looks chimerical from a Wittgensteinian standpoint, and you have reasons for doubting (sorry!) whether the Method should "be taken entirely seriously". No matter. What's important as a takeaway here is that JTB+U is a contribution to understanding "the actions of life", the actions of practice-governed justification.

As for Williams' defense of the validity of Descartes's radical doubt: It hinges on the distinction Williams makes between "the universal possibility of illusion" and "the possibility of universal illusion." Descartes believes that "it is epistemically possible that all supposedly perceptual judgments are mistaken," and Willams points out that "the strict contradictory of a perceptual judgment is not itself a perceptual judgment." What he calls "the everyday negation" of a statement like "There is a table in front of me" is a contrary, not a contradictory -- that is, it translates as "What is in front of me is not a table." So radical doubt is only senseless if misunderstood as "the universal possibility of illusion."

Williams's book is a great read, but I don't want to belabor Descartes.

I can accept inner understanding as real, while still insisting that justificatory standing isn’t a private feeling and can’t be reduced to a report of how things seem. The practice-governed side is what I’m trying to keep in view. — Sam26

Good. My only reason for introducing the experiential aspect of "understanding" was to ground it in what we might call "mental practice," something we do, in a different sense from "what we do" in the practice of justification. But an inquiry into that aspect of understanding would be a type of phenomenology, governed by the public guardrails you outline.

Good, I’m happy with the way you’ve positioned JTB+U as an account of practice-based justification rather than something Cartesian. I also like Williams’s distinction between the actions of life and the search for truth, and I agree, for my purposes, the Method isn’t the standard by which ordinary knowing should be measured.

As for Williams’s: I see the distinction you’re drawing, universal illusion versus the possibility of universal illusion, and the point about strict contradictories versus everyday negations is helpful. It shows why some crude formulations of “everything might be false” are incoherent, and why the radical doubt needs to be stated carefully if it’s to have content. Still, from my Wittgensteinian angle, the pressure doesn’t entirely disappear. Even if the negations can be stated coherently, the question remains whether the skeptical posture can be sustained without borrowing the very criteria of correction that it's trying to bracket. That’s not a refutation of Williams, it’s just to say that I’m inclined to treat the Method as a philosophical exercise with a special aim, not as an account of doubt that illuminates ordinary justification.

I agree with your last point about understanding. I’m not trying to eliminate the experiential aspect of grasping. If you want to talk about “mental practice,” I’m open to that. My point is that whatever phenomenology we offer still has to be disciplined by the same kinds of constraints we’ve been discussing, i.e., it needs criteria for what counts as getting it right, what counts as misdescription, what would count as correction, and what would count as defeat. In that sense, even an inquiry into inner understanding isn’t purely private. It’s still answerable to practice-governed standards, even if its data are first-person. That’s a nice way to connect your point back to the thread without letting it drift into an uncheckable subjectivism.

Williams’s distinction between the actions of life and the search for truth — Sam26

This is actually Descartes's phrase -- quite a prescient distinction for a 17th century person!

Even if the negations can be stated coherently, the question remains whether the skeptical posture can be sustained without borrowing the very criteria of correction that it's trying to bracket. — Sam26

Yes. The first step is to rescue Descartes from incoherence, and then his defender has to take a position on the "criteria of correction" that separates them out from ordinary justifications. I agree that Williams doesn't have the last word here.

I’m inclined to treat the Method as a philosophical exercise with a special aim, not as an account of doubt that illuminates ordinary justification. — Sam26

Absolutely. And again, philosophers will differ on whether that special aim really makes sense. Descartes thought he had discovered something about the connection of knowledge and incorrigibility. But had he? I think that depends entirely on how convincing one finds the cogito. My own take, in a sentence, is that the cogito tells me that I am, but not what I am -- what "I" is. Well, enough of that. :smile:

I agree with your last point about understanding. I’m not trying to eliminate the experiential aspect of grasping. If you want to talk about “mental practice,” I’m open to that. My point is that whatever phenomenology we offer still has to be disciplined by the same kinds of constraints we’ve been discussing, i.e., it needs criteria for what counts as getting it right, what counts as misdescription, what would count as correction, and what would count as defeat. In that sense, even an inquiry into inner understanding isn’t purely private. It’s still answerable to practice-governed standards, even if its data are first-person. That’s a nice way to connect your point back to the thread without letting it drift into an uncheckable subjectivism. — Sam26

Yes indeed. How far can the basic "bracketing" move take us away from our experiences as intersubjective/public intelligences? While it's correct that only I can supply the first-person data that would confirm or deny whether "I am now thinking of a purple cow" is true, it remains the case that getting this right, even in the privacy of my own mental home, means accepting the same public criteria we'd need for an actual purple cow. And all the more so when we turn to the much more complicated case of understanding.

Coninuing with paper...
Post #2

Introduction

The classical model of knowledge as JTB has remained a durable point of reference in epistemology. Its appeal lies in its clarity. To know something is to hold a true belief that stands within an appropriate practice of justification. The model is simple without being simplistic. It expresses a structure that is familiar in ordinary life. When we claim to know something, we ordinarily take ourselves to have a belief that is true and properly supported. For this reason, JTB has persisted as a natural starting point for thinking about knowledge.

The simplicity of the classical model can, however, obscure features of our epistemic life that play a quiet but indispensable role. Our practices of justification do not occur in isolation. They take place within shared language-games, where words already have their use and where standards of assessment are already in place. These practices depend on a background of bedrock certainties that lie outside the space of knowing and doubting. Such certainties mark where justification comes to an end and reveal the background against which our epistemic concepts have their life.
A further feature of our epistemic practices is that justification requires more than the presence of supporting grounds. It requires the ability to use our concepts correctly within a form of life. This ability is not something added to justification from the outside. It is internal to justification itself. Understanding, in this sense, belongs to the grammar of knowing. When understanding is absent, a belief may appear well supported but still fail to count as knowledge, because it does not stand in the right way within a practice of justification.

Contemporary discussion often treats Edmund Gettier’s examples as showing that the classical model is inadequate. I do not think this is the right lesson. These cases do not expose a defect in JTB itself. They trade on a confusion between beliefs that merely appear justified and beliefs that are genuinely justified within a practice. They also assume a picture of justification that exceeds anything governing ordinary epistemic life, as though the appearance of support were enough to settle matters conclusively. Once we attend carefully to how justification functions, including its graded and fallible character, these examples lose the weight they are often given. They rest on a distorted conception of justification, not on a flaw in the classical model.

These considerations suggest that the classical model can be refined without abandoning its core insight. I develop this refinement in terms of JTB+U, which retains truth, belief, and justification while making explicit the role understanding plays within a practice of justification. Truth remains the condition that marks the success of a belief. Belief continues to mark commitment. Justification continues to name the standing a belief must have within shared epistemic practices. The refinement lies in bringing into view the conceptual competence that justification presupposes and the background of certainties that allows it to function.

To make this more concrete, I outline five routes through which justification typically proceeds in everyday life: testimony, logic, sensory experience, linguistic training, and pure logic in its boundary-setting role. These routes are presented in the order in which they most often appear in our language-games, not as a hierarchy of epistemic importance. Alongside these routes, I describe three guardrails that structure our practices of justification: No False Grounds, Practice Safety, and Defeater Screening. Together, they express the discipline internal to justification rather than an external checklist imposed upon it.

Later sections examine the role of bedrock certainties more closely and consider a structural parallel between Wittgenstein’s treatment of hinges and Gödel’s limit results. I also distinguish the expressive from the epistemic use of “know,” a distinction that clarifies how hinge commitments operate outside the space of justification. In closing, I consider how this Wittgensteinian extension of JTB bears on our current epistemic environment, including the status of claims made by artificial systems. My aim is not to replace the classical model, but to show how it can be clarified once these background features are brought into view. The result is an account of knowledge that remains continuous with the classical tradition and better aligned with the practices in which our epistemic standards are at home.

Yes, I think we agree, and I like the way you’ve put it. Even in first-person cases, the privacy is about access to the data, not about private standards. If I report “I’m thinking of a purple cow,” only I have immediate access to that episode, but what makes the report intelligible as correct or incorrect still depends on shared criteria for what “purple,” “cow,” “thinking,” and “now” mean. Otherwise, the report collapses into something like a mere noise, insulated from proper assessment.

That’s exactly why I’m willing to talk about “mental practice” while still resisting uncheckable subjectivism. First-person data can be real, but the terms we use to describe it still have to be disciplined by criteria of correct use, misdescription, correction, and defeat. When we turn to the more complex case of understanding, the same point intensifies. It’s not enough to say “I understand” as a private feeling. The claim earns standing by how it shows up in competence: tracking mistake-conditions, handling counter cases, recognizing defeaters, and making the right corrections when error signals appear.

So yes, I think your bracketing question is correct. The more we try to pull meaning and assessment entirely into the private sphere, the more we lose the very distinction between getting it right and merely seeming right, and that distinction is exactly what justification, and understanding are supposed to preserve.

Coninuing with paper...

Post #3

1. The Classical Model and Its Enduring Appeal

The classical model of knowledge as justified true belief has served as a central framework because it captures something steady in our epistemic practices. When we say that someone knows something, we normally take the claim to involve a true belief that is supported within a practice of justification. The structure is not artificial. It mirrors the way we distinguish between mere belief and belief that has a secure place in our shared life. In this respect, JTB remains a natural starting point for thinking about knowledge.

The appeal of the model is strengthened by how easily it fits the examples that shape our everyday assessments. In ordinary contexts we do not treat knowledge as rare or fragile. We routinely take ourselves to know many things and rely on others to know as well. The classical model reflects this confidence. It expresses a pattern in which truth, belief, and justification work together to mark out the space in which epistemic claims have their home. When each element is in place, we are usually content to say that someone knows what they claim to know.

Much of the contemporary discussion treats Gettier’s paper as showing that JTB is insufficient. I do not think this is the right lesson. The examples do not undermine the model itself. They depend on a confusion between what looks justified on the surface and what is genuinely justified within a practice. Once we attend to the structure of justification, including its graded and fallible character, it becomes clear that these cases fail to satisfy the justification condition in the first place. They rest on false grounds or on a lack of the relevant conceptual competence, and so they fall outside the classical model rather than threatening it. Seen in this way, Gettier does not overturn JTB; it signals the need to make explicit features of justification that the classical formulation left implicit. That is the task taken up by JTB+U in the sections that follow.

Worked Gettier example (diagnostic use). Consider the familiar “ten coins” case. Smith has strong evidence that Jones will get the job, and Smith has counted ten coins in Jones’s pocket. Smith forms the belief, “The man who will get the job has ten coins in his pocket,” by straightforward logical inference from what he takes himself to know. Unknown to Smith, Jones will not get the job. Smith will get the job, and Smith also happens to have ten coins in his own pocket. The belief is true, and it can look well supported, but it does not have the standing required for knowledge.

What fails is not truth, and not belief, but justification. The support Smith relies on depends on what is not the case, namely that Jones will get the job, and this triggers No False Grounds. One can say that Smith’s inference is valid, but validity is not enough, because justification is not merely a logical relation among propositions. It is a standing within a practice, fixed by public criteria that settle what counts as competent support in the context. The same case also brings Practice Safety into view. Smith stumbles into the truth by luck. In ordinary situations where the evidence is similar, he would draw the same conclusion, yet it would be false, so the belief is not practice safe. Defeater screening makes the point plain: once it is determined that Jones may not get the job, the belief loses its standing, and the only repair is to replace the faulty ground. Gettier does not refute JTB, it corrects a picture of justification as a private sense of assurance or a merely formal inference, rather than a public standing fixed by our epistemic practice.

Coninuing with paper...

Post #4

2. Bedrock Certainties and the Grammar of Doubt

Our practices of justification presuppose a background that is not itself the product of justification. Certain claims stand fast for us, not because we have examined them and found them secure, but because they form part of the setting in which doubt and inquiry take place. Wittgenstein’s remarks in On Certainty help bring this structure into view. These certainties are not items of knowledge, nor are they justified by appeal to further grounds. They are the conditions under which epistemic justification has its life. In this sense they are foundational, though not in the familiar epistemic sense. They do not support our judgments by supplying evidence. They show the limits within which justification makes sense.

Calling them “certainties” can be misleading unless we are careful. They are not the product of conviction or assurance, and they are not secure because they satisfy some heightened epistemic standard. Their stability is grammatical rather than epistemic. They show themselves in what we do, in what counts as checking, correcting, and going on, rather than being items we first establish and then build upon. They reflect what we do not call into question when we assess claims within a practice. To doubt them is not to extend inquiry but to disrupt the language-game in which inquiry occurs. They do not stand as privileged beliefs but as elements of our form of life that make belief and doubt possible.

These certainties are not all on the same level. Some are so deeply woven into our life that they scarcely appear as propositions at all: that there is a world, that objects persist, that our memories normally serve us. Others reflect the training we inherit: how to use a word, how to identify an object, how to follow a rule. Still others are tied to domains of practice: the reliability of an instrument, the stability of a method, the way evidence is handled in a field. These layers differ in depth and scope, but they share a common role. They stand fast for us in ways that are not themselves open to epistemic assessment. They shape the riverbed against which justificatory flow is possible.

Belief is not exhausted by what we say. A belief can be expressed in a statement, but it can also be shown in action, in what we treat as settled, in what we rely on without question, and in what would count as a mistake. In that sense, hinges can be called beliefs, not because they are conclusions supported by justification, but because they are displayed in the way we live and inquire. They are part of the background that shapes our practices of justification, and they show themselves in the fact that we go on as we do.

This is also why meaning as use matters for epistemology. The concept of knowledge does not float above our language-games as a definition waiting to be discovered. Its grammar is shown in how we use the word “know” across a range of cases. The uses are not identical, and they do not form a tidy essence. They exhibit family resemblance. Yet this variation does not imply relativism. It shows that the stability of the concept lies in the rules of its use, in what counts as justification, correction, and withdrawal within the practices that give the word its life.

Understanding the role of these certainties also clarifies the relation between knowing and doubting. Doubt always presupposes a background that is not in doubt. To question everything is not a form of radical inquiry; it is the loss of any standpoint from which inquiry can proceed. Our doubts and our claims to know both operate within a structure that is taken for granted, not as an expression of conviction but as part of the grammar of our practices. This is why hinges cannot be treated as knowledge or as hypotheses waiting to be confirmed. They are neither. They are the background against which the contrast between knowledge and error has meaning.

This non-epistemic foundation does not conflict with the classical model of knowledge. On the contrary, it clarifies how the model functions within a form of life. Justification can do its work only because something stands fast. To bring this into view is not to replace the classical model but to make explicit what it already presupposes. The refinement developed in JTB+U rests on this point. By acknowledging the structure of bedrock certainties, we can make clearer how justification operates and why it has the limits it does. These limits do not diminish our epistemic practices; they make them possible.

These layers differ in depth and scope, but they share a common role. They stand fast for us in ways that are not themselves open to epistemic assessment. They shape the riverbed against which justificatory flow is possible. — Sam26

A possibly interesting question occurred to me, reading this. Most sophisticated theology would maintain that the existence of God is certain, but not open to epistemic assessment, or at least not any assessment that would resemble ordinary justification. Is there any reason not to accept such a claim, along with claims like "There is a world" and "Objects persist"?

One natural reply is, "But there being a world, and objects persisting, are essential parts of how we play the game of justification. Their 'grammatical certainty' is evident. This is not the case with 'God exists'. We can do all the things we need to do in our practice-based justification without needing 'God exists' to be certain or even true."

So this may be the often unacknowledged basis for building a structure of rational theology. The theologian hears this reply and responds, "Very well. You've challenged me to show you why 'God exists' is indeed part of the grammar of rational justification." And from this we get, for instance, Thomism, or a Plantinga-like "analytical theism."

My point is that the wish to show the necessity of God to human existence is, oddly, in harmony with the wish to establish certainties that define our practices. Whether the theologian succeeds is of course another matter.

That’s an interesting question (I've thought about this because there are increasingly more people who want to treat "God exists" as a hinge), and I think the “natural reply” you gave is basically right: some certainties are hinge-like because they’re built into the grammar of ordinary justificatory practice. “There is a world,” “objects persist,” “memory is generally reliable,” and so on are not conclusions we reach by evidence, they’re part of what makes evidence, error, correction, and inquiry possible at all.

My caution is this. People are increasingly tempted to treat “God exists” as a hinge, but we have to be careful about what a Wittgensteinian hinge is. A hinge isn’t merely a proposition someone holds with great confidence, and it isn’t simply a belief a community cherishes. A hinge is a standing-fast commitment that is displayed in the practice in such a way that ordinary doubt about it doesn’t have a stable role. In that sense, hinges are tied to the language-game of doubting: they mark the background against which doubt and justification can get traction, and that’s why they aren’t ordinarily subject to epistemic inquiry.

Belief in God doesn’t function like that for most of us, even for many believers. It's very much a live topic of doubt, dispute, argument, conversion, deconversion, and counterargument. If “God exists” is treated as hinge-certain in the same way as “there is a world,” it risks becoming a category mistake: it treats a contested metaphysical claim as if it were a background condition of inquiry.

Now, you’re right that sophisticated theology often wants something like hinge-status: not just “God exists” as a hypothesis, but “God exists” as a necessary condition for rationality, morality, or intelligibility. That’s exactly the Thomist or analytic theist move you’re describing: to argue that God isn’t merely one more claim inside the system, but part of what makes the system possible.

My point is: that’s a coherent aspiration, but it’s also a very high bar. To succeed, the theologian would have to show that the denial of God undermines the grammar of justification itself, not just that God is a good explanation, or a satisfying metaphysical picture. And until that bar is met, “God exists” looks less like a hinge and more like a substantive claim that remains open to epistemic assessment, including defeaters, alternatives, and the usual standards of practice.

I’d put it this way: the desire to make God hinge-certain is structurally parallel to the hinge idea, but whether it earns hinge status depends on whether it can be shown to be a condition of intelligible justification, rather than a powerful thesis within a wider field of disputable metaphysics. I don't think it works as a hinge.

In looking at the snippets of the paper you have been slowly unleashing, I’ve been trying to place its core method and approach with respect to the philosophical communities I am familiar with. What is its relation to poststructuralism, phenomenology, hermeneutics, Criitical theory, American pragmatism, and figures like Merleau-Ponty, Gadamer, Dilthey, Dewey and Peirce? It seems to me your perspective aligns most closely with the work of post-Sellarsians like Robert Brandom, John Mcdowell and Donald Davidson, who draw centrally from Kant and Hegel, and all but ignore the post-Hegelian approaches to reason, justification and ground offered by these other communities.

You make frequent mention of the later Wittgenstein, but you force him into the post-Sellarsian ‘space of reasons’ box occupied by Brandom, Pippin, MacDowell and other Pittsburgh school Hegelians, and strip away the hermeuneutic and phenomenological elements which make his work so different from the Hegelians. Not that there’s anything wrong with that, but If you haven’t read Brandon, you might find his approach to be a better fit for what you’re going after than the later Wittgenstein.

In looking at the snippets of the paper you have been slowly unleashing, I’ve been trying to place its core method and approach with respect to the philosophical communities I am familiar with. What is its relation to poststructuralism, phenomenology, hermeneutics, Criitical theory, American pragmatism, and figures like Merleau-Ponty, Gadamer, Dilthey, Dewey and Peirce? It seems to me your perspective aligns most closely with the work of post-Sellarsians like Robert Brandom, John Mcdowell and Donald Davidson, who draw centrally from Kant and Hegel, and all but ignore the post-Hegelian approaches to reason, justification and ground offered by these other communities.

You make frequent mention of the later Wittgenstein, but you force him into the post-Sellarsian ‘space of reasons’ box occupied by Brandom, Pippin, MacDowell and other Pittsburgh school Hegelians, and strip away the hermeuneutic and phenomenological elements which make his work so different from the Hegelians. Not that there’s anything wrong with that, but If you haven’t read Brandon, you might find his approach to be a better fit for what you’re going after than the later Wittgenstein. — Joshs

That’s a fair attempt to place the paper, but I'll make my goal simpler. Mostly what I’m doing is starting with the classical JTB framework and then modifying it with Wittgenstein’s later thinking.

The center of gravity isn’t Brandom or a “space of reasons” program, and it isn’t a grand map of poststructuralism, phenomenology, hermeneutics, or critical theory. The point is narrower and more practical: JTB is a useful starting grammar for “knowledge,” but it tends to invite a thin picture of justification, as if justification were exhausted by citeable supports. Wittgenstein helps me clarify what J is doing in real epistemic life: justification has a role within practices, it is disciplined by standards of error and correction, it relies on background certainties that “stand fast,” and it can’t be made into an all-purpose demand for absolute certainty.

That’s also why I added “+U.” It’s not an extra ingredient bolted onto JTB. It’s a way of making explicit something that’s often left implicit in how justification actually works: the competence to track mistake-conditions, defeaters, and correction, so we don’t confuse the appearance of support with genuine justificatory standing.

If there are affinities with pragmatism or with later analytic work on normativity and practice, I’m happy to acknowledge them. But I’m not trying to force Wittgenstein into Hegelian inferentialism. I’m using later Wittgenstein to keep JTB anchored in how our practices actually operate, and to keep the discussion aimed at epistemic certainty, not Cartesian absolute certainty.

Coninuing with paper...

Post #5

3. The JTB+U Refinement

Truth remains the condition that marks the success of a belief within a practice. To say that a belief is true is simply to say that the world is as the proposition represents it. I do not offer this as a theory of truth but as part of the grammar of our concept of knowledge. Nothing in the refinement developed here alters this point. What changes is not the truth condition but our understanding of how justification functions within a practice and what it presupposes.

As my teacher Dr. Byron Bitar often emphasized, “know” is a success word: it applies only when a belief has succeeded in being true. The point is grammatical rather than theoretical. To call something knowledge is to mark that the proposition stands as things are and that the belief stands properly within a practice of justification.

The classical formulation of knowledge as justified true belief identifies the core elements that shape our epistemic practices. What it leaves implicit is the internal structure of justification, the conceptual competence required for it, and the background of certainties that allow it to function. The refinement I call JTB+U does not add a new condition to the classical model. It brings into clearer view the role of understanding within justification and the constraints that govern how justification proceeds within a practice. Truth and belief remain as they are. What changes is our grasp of the conditions under which justification has its place.

Understanding is not an optional supplement to justification; it is internal to it. To justify a belief is to use the relevant concepts correctly, to navigate their connections, and to appreciate how they function within the language-game in which the claim is made. A belief can have the appearance of support while lacking this internal structure. In such cases, failure is not an external defect but a grammatical one. The belief does not stand within the practice in the way it appears to. JTB+U makes explicit that justification requires this kind of conceptual competence, and without it the belief is not justified, even if it appears well grounded on the surface.

Nothing in this account requires absolute certainty or infallibility. The certainty involved in knowledge is not the logical or metaphysical certainty sometimes assumed in discussions of justification, but the epistemic certainty appropriate to a practice, that is, a defeater-resistant standing within established norms of assessment. A belief may fail to constitute knowledge without any demand for infallibility having been violated. What is missing in such cases is not certainty in the absolute sense, but the kind of justificatory standing that allows a belief to function as settled within an epistemic practice. Gettier cases trade on a tacit slide from epistemic certainty to absolute certainty, treating the failure of the latter as evidence that justification was never genuinely in place. JTB+U blocks this slide by preserving fallibility while insisting that genuine justification must still confer the sort of certainty that marks a belief as properly held within its epistemic context.

A useful comparison can be drawn here with the familiar distinction between syntax and semantics, often emphasized in discussions of artificial intelligence. As John Searle has argued, a system may manipulate symbols in a formally correct way without thereby grasping their meaning. The parallel in epistemology is not exact, but it is instructive. A person may produce correct statements, cite appropriate considerations, or even follow valid patterns of inference, while lacking an adequate grasp of the concepts involved or of the justificatory relations that give those considerations their standing. Understanding, as it figures in JTB+U, marks this difference. It is not an inner state added to justification, but the competence displayed in using concepts correctly within a linguistic practice, in recognizing what supports what, and in seeing what would count as a mistake. Unlike Searle’s contrast, however, this distinction is not all-or-nothing. Understanding admits of degrees, and epistemic failure often consists not in its absence but in its fragmentation or misapplication. This is why justification can appear to be present while still failing to confer knowledge: the syntax of justification is in place, but its grammar has not been fully grasped.

The role of understanding within justification should not be mistaken for a call for greater formalization, or for something that could be captured by adding further logical or mathematical conditions. Formal models can be useful for clarifying constraints and dependencies, but they abstract away from the language-games and forms of life in which epistemic concepts have their use. When this abstraction is mistaken for an account of justification itself, justification is reduced to a relation among propositions rather than a standing within a practice. The same mistake underlies the temptation to treat definitions of truth as explanatory foundations rather than as grammatical reminders. In JTB+U, logic retains its proper place as a tool for clarification and boundary-setting, but justification and understanding remain internal to the practices in which believing, correcting, and withdrawing claims have their life. To detach them from those practices is not to strengthen the classical model, but to empty it of the very grammar that gives it sense.

Wittgenstein’s point can be put another way. If we try to treat understanding as an inner item, something to which one privately points as the basis of one’s epistemic standing, we lose the grammar of justification. The beetle in the box is the warning. If what is supposed to ground a claim is sealed off from the public criteria of the practice, then whatever it is, it cannot do the justificatory work we require of it. Justification depends on what can be shown in the language-game, on what counts as correct use, correction, and withdrawal. When we detach support from those criteria and relocate it in the private interior, we have not strengthened knowledge. We have removed it from the practice in which “know” has its use.

This point is reinforced by the various ways in which we justify beliefs in everyday life. These routes are not ranked, nor do they form a hierarchy. They reflect the ordinary movement of our practices. We justify beliefs through testimony, through patterns of reasoning, through sensory experience, through the linguistic training that shapes our use of concepts, and through pure logic in its boundary-setting role. These routes differ in form but not in status. They do not compete for epistemic priority. They mark out the ways in which justificatory support can be given within different contexts of assessment.
Each route is governed by constraints that help maintain the stability of our epistemic practices. A belief cannot be justified if it rests on false grounds. It must be safe within the practice, meaning that its support remains intact under ordinary scrutiny. And it must stand free of undefeated challenges. These constraints do not form an external checklist. They articulate the discipline internal to justification. They describe what it is for a belief to stand within a practice in a way that warrants the attribution of knowledge.

Taken together, these features clarify the refinement offered by JTB+U. The classical model remains intact, but we gain a sharper view of the background grammar that governs justification and the conceptual competence that allows it to function. What appears to be a new condition is better understood as a description of what justification already requires. The refinement is not an alteration of the model but an articulation of its underlying structure. Knowledge remains true belief that stands within a practice of justification. JTB+U helps us see more clearly what it is for a belief to stand there.