Comments

  • Fitch's "paradox" of knowability
    It's "know that P", not "know of p".Banno

    I don't see that it matters.

    Is there any reason/argument why "¬Kp" can only mean that p's truth value is unknown, and not that the sentence p is unknown?Luke
  • Fitch's "paradox" of knowability
    So this proposition: "there are x number of blades of grass in the world and nobody believes it" is true. Yet it can't be known to be true.
    — Bartricks

    Then how do you know that "there are x number of blades of grass in the world and nobody believes it" is true?
    — Luke

    I don't. No one can. That's the point.
    Bartricks

    But you said that it was true? I'm asking how you know that in the first place before you tell me that it can't be known to be true.
  • Fitch's "paradox" of knowability
    So this proposition: "there are x number of blades of grass in the world and nobody believes it" is true. Yet it can't be known to be true.Bartricks

    Then how do you know that "there are x number of blades of grass in the world and nobody believes it" is true?
  • Fitch's "paradox" of knowability
    Is there any reason/argument why "¬Kp" can only mean that p's truth value is unknown, and not that the sentence p is unknown?

    Doesn't "p" entail that p is true?
  • Fitch's "paradox" of knowability
    ...not in the SEP version...

    it seems to me to use Kp as knowing p, not knowing of p...
    Banno

    That's the assumption that I'm challenging. Simply asserting that assumption is not an argument.
  • Fitch's "paradox" of knowability
    Well, no they're not. Demonstrably. For instance, take the proposition 'X is the case and nobody believes X'. Well, that can be true. But it can't be known to be true.Bartricks

    It can be true, but is it true? The argument speaks only of possible knowledge (of true statements), not of possible truth.
  • Fitch's "paradox" of knowability
    In truth, I had failed to notice that the Wiki argument uses the wrong assumption. Too much faith in Wiki, I guess.Banno

    Where does it use the wrong assumption?

    SO you accept the assumption ∀p (p → ♢Kp) but not the conclusion ∀p (p → Kp)?Banno

    I accept the conclusion, but there is an equivocation whether Kp means knowledge of the sentence or knowledge that the sentence is true.
  • Fitch's "paradox" of knowability
    Line 3. It's a conclusion, not an assumption. Hence the paradox.Banno

    You said that it wasn't part of Fitch's paradox. Anyway, I agree that it is impossible to know an unknown sentence. You appeared to be arguing that it was possible only a few posts back. I'm not disputing the argument or its conclusion. I am only disputing the assumption regarding its conclusion: that knowability implies knowledge of all (known and unknown) true statements.
  • Fitch's "paradox" of knowability
    And what about ◊K(p∧¬Kp)?
  • Fitch's "paradox" of knowability
    What does "¬Kp" refer to there?
  • Fitch's "paradox" of knowability
    rather, I don't see where you think this fits into the Fitch argument.Banno

    Read the OP and see the Wikipedia proof given there (or see Janus' partial quote above). I am following its use of an unknown p.
  • Fitch's "paradox" of knowability
    Oh I see. I take it you're no longer arguing that it's possible to know an unknown sentence?
  • Fitch's "paradox" of knowability
    Was there a point to your question?
  • Fitch's "paradox" of knowability
    What are your views on K(P) → KP?Agent Smith

    I don't disagree with the conclusion of Fitch's argument, but I don't interpret it to mean that knowability implies the superhuman knowledge of all (known and unknown) true statements, either.
  • Fitch's "paradox" of knowability
    There might be a teapot in orbit around Jupiter.

    You know the sentence "there might be a teapot in orbit around Jupiter"

    You do not know if there is a teapot in orbit around Jupiter.

    Hence you know an unknown sentence.
    Banno

    If I know the sentence, then how is it an unknown sentence?

    IF you don't like the teapot example, substitute any other unknown assertion.Banno

    No such example can be given. As the Wiki article tells us:

    ...if all truths are knowable, the set of "all truths" must not include any of the form "something is an unknown truth"Fitch's paradox of knowability
  • Fitch's "paradox" of knowability
    Then I will offer a specific example of p:

    1. if the Riemann hypothesis is true then it is possible to know that the Riemann hypothesis is true
    2. we don't know that the Riemann hypothesis is true
    3. if the Riemann hypothesis is true and we don't know that the Riemann hypothesis is true then it is possible to know that the Riemann hypothesis is true and that we don't know that the Riemann hypothesis is true

    It is a fact that we don't know that the Riemann hypothesis is true – it's one of the more significant unproven problems in mathematics. Therefore, we must reject the knowability principle.
    Michael

    What if the Riemann hypothesis is false? Then we do not reject 1. It is not enough that we don't know whether p is true; it must also be true. "p" means/entails "p is true". This is where the equivocation lies.

    ¬Kp could mean that we don't know the content/meaning of p and/or that we don't know the truth of p; that we don't know the Riemann hypothesis and/or that we don't know that it is true.
  • Fitch's "paradox" of knowability
    Must get to bed. I'll respond further tomorrow.
  • Fitch's "paradox" of knowability
    We don't know that p is true in this case.Michael

    That's what I'm disputing about the argument. This is the equivocation I'm talking about.
  • Fitch's "paradox" of knowability
    Suppose p is a sentence that is an unknown truth; that is, the sentence p is true, but it is not known that p is true.Fitch's paradox of knowability
  • Fitch's "paradox" of knowability
    2. the truth value of p is unknownMichael

    It's not the truth value of p which is unknown, because we know that p is true. It is the true statement, p, which is unknown.
  • Fitch's "paradox" of knowability
    Logic is really bad at doing time. Truths have to be eternal. That p is an unknown truth is unknowable until p is known, and then it is not an unknown truth. the difficulty arises because knowability implies time.unenlightened

    I agree with you completely on this.

    This is the heart of darkness - suppose we know something that we suppose we do not know. "the 79 squillionth decimal iteration of pi is a '2'." Well do we know or don't we? Make up your mind, Fitch. The digit is knowable, but 'that it it 2' is knowable only if it happens to be 2, which we don't know. p0, p1... p9 - one of them is an unknown truth, and the others are unknown falsehoods.unenlightened

    That we do and/or do not know something is not about the same sort of temporal possibility/knowability that you describe above. To "suppose we know something that we suppose we do not know" just seems like a pure contradiction.
  • Fitch's "paradox" of knowability
    Yes, and as the knowability principle is the principle that p is true if it is possible to know that p is true it then follows from what you say here that every true statement is known to be true.Michael

    I think the argument implies that every known true statement is known to be true:

    ,,,as soon as we know "p is an unknown truth", we know that p is true, rendering p no longer an unknown truth, so the statement "p is an unknown truth" becomes a falsity. Hence, the statement "p is an unknown truth" cannot be both known and true at the same time. Therefore, if all truths are knowable, the set of "all truths" must not include any of the form "something is an unknown truth"; thus there must be no unknown truths, and thus all truths must be known.Fitch's paradox of knowability

    As I said in the OP, this excludes all unknown statements and statements with unknown truth values.
  • Fitch's "paradox" of knowability
    However, the knowability principle entails that if it is true then I know that it is true, which contradicts the non-omniscience premise.Michael

    My view is that if it is a true statement, then it cannot be unknown that it is a true statement (see the Wiki quote again). And that's because in order for it to be possible to know that it is true, we must first know the statement and what it means. If it is possible to know that p is true, then we must know that p (is true), And the truth of the statement is presupposed.
  • Fitch's "paradox" of knowability
    But we don't know which of the statements is true, which means that we must reject the knowability principle.Michael

    That's not Fitch's argument, which assumes the truth of p. It's not that we don't know which statement is true (and which is false); it's that we don't know the statement that is true. So, which of those statements (about the box) is true?
  • Fitch's "paradox" of knowability
    Given this contradiction we must either reject the knowability principle or accept that we know which of "the box is empty" and "the box is not empty" is true.Michael

    I would say that we (now) know both of these statements, particularly since you have stated them. However, Fitch's argument speaks only of our knowledge - or lack thereof - of true statements.

    The argument says that if it is possible to know a true p, then we must know that p is true. I argue that this is not due to our knowledge of p's truth, but due to our knowledge of p: If it is possible to know a true p, then we must know what p states. That is, my point is that the argument equivocates on knowledge of p (i.e. knowing what p states) and knowledge of p's truth value. Btw, I don't disagree with the argument's conclusion. I just don't see it as implying that we must know the truth of any proposition. The argument refers only to those propositions that are true in the first place.

    Therefore if we insist on the knowability principle then we must accept that every true statement is known to be true.Michael

    I'm curious: do you reject the knowability principle or do you believe that the argument's conclusion endows us with knowing the truth value of every proposition? I don't reject the knowability principle. On what grounds would you?
  • Fitch's "paradox" of knowability
    Thanks for your responses.

    The other point that's up for discussion is that somewhere in Fitch's argument, K(P) → KP where K(P) means P is knowable and KP means Known that P. Feels like an illegal move to me.Agent Smith

    I'm not arguing along these lines, but I would be interested in an argument for it.

    An example: I know that calculus is knowable, but that hasn't helped me at all, I haven't the slightest clue what calculus is about. :snicker:Agent Smith

    I'm not sure I would agree. As the WIki article notes, p is a sentence or a proposition. Such sentences are typically truth apt. I don't consider a field of study, such as calculus, to fit the bill of a truth-apt proposition.
  • Is there an external material world ?
    It seems instead to me that materialism is an idea which can never be verified, as for it to be verified, it would require proving that there is something existing independently of conscious beings.Hello Human

    Don't you exist independently of other conscious beings? Since those conscious beings each have material bodies, then there is something material which exists independently of you: other people. Otherwise, do you assume that we are each free-floating consciousnesses without material bodies?
  • Does nothingness exist?
    it makes a difference whether something or nothing is being intuited or thought.Jackson

    Does this refer to thinking about nothing or not thinking?
  • "What is it like." Nagel. What does "like" mean?
    So you, I and the bat all see the moth.Banno

    What is it like to see a moth?

    It's not at all uncommon to find folk claiming that because the bat sees the moth differently, there is no moth.Banno

    You could say that what it is like for a bat to see a moth is different from what it is like for a human to see a moth.

    One explanation of "what it is like" might be "how it feels"; not only in an emotional sense, but also in sensory terms of (how it) looks, sounds, tastes, smells, proprioception, temperature, balance, etc.
  • Why are things the way they are?
    Efficient cause answers the question of what particular event(s) conspired to trigger the observed result. So it sits with material cause (as the material potential which could be the substance partaking in the change) down at the "how" end of things.apokrisis

    I admit to being not very familiar with Aristotle's Four Causes, but the Wikipedia article on the topic associates efficient cause with an Agent:

    Agent (the efficient or moving cause of a change or movement): consists of things apart from the thing being changed or moved, which interact so as to be an agency of the change or movement. For example, the efficient cause of a table is a carpenter, or a person working as one, and according to Aristotle the efficient cause of a child is a parent.Wikipedia article: Four Causes

    It seems to me as though this (Agent, efficient cause) would be the sort of cause that god is, and possibly evolution too? In my previous posts I identified god and evolution as possible answers to the question of why the brain produces qualitative experiences, as opposed to the question of how the brain produces qualitative experiences.

    Perhaps "how" and "why" are rather rough and ready folk terms when it comes to analysing causality? So the better thing to do is move on and only employ the technical categories of Aristotle's metaphysics?apokrisis

    Perhaps, but I was querying the distinction between "how" and "why" questions and whether "why" questions are necessarily questions of causality.

    If you get the right causal language, causation should start to seem more common sense and not so dualistically divided between world and spirit, or whatever.apokrisis

    As an atheist, the only intelligent design I believe in is the type found in the creations of humans and other animals, so I don't have this problem.
  • Things That We Accept Without Proof
    It's a relief to me that someone groks the 'uselessness' of qualia I'm trying to sketch. It's so 'obvious' eventually and yet so absurd on the face of it.lll

    It's great to know I'm not the only one who reads him this way! Little is more seemingly absurd than "it's not a Something, but not a Nothing either!"

    The later Wittgenstein only seems boring to those who aren't ready. What say you?lll

    Definitely. Back to the rough ground!
  • Why are things the way they are?
    What I was questioning and what I poorly attempted to articulate in the OP was supposed to be whether there is a particular set of "why" questions that cannot be answered any further than by responding that this is just the way things are.

    I have noticed this particular "why" question crops up repeatedly in various guises in philosophy.
    — Luke

    It's the search for a causal account.
    apokrisis

    I was questioning whether such "why" questions are always a search for a causal account. I see now that I had been thinking of a causal account only in terms of "how" questions. As I said previously, knowing all the causes of how the brain produces qualitative experience does not touch the question of why we have those qualitative experiences. However, you are right that I had overlooked the causal account given by a final (or efficient?) cause. After completely accounting for how the brain produces qualitative experiences, the question of why we have qualitative experiences could be accounted for in terms of god or evolution. It could then be asked why god or evolution exist, but these seem like further "how" questions.

    Admittedly, I'm still a bit unclear on the difference, if any, between "how" and "why" questions, but this is helpful:

    ‘Why’ questions look for an overarching explanatory scheme to organize particular facts or subordinate the patterns.Joshs

    :up:

    @180 Proof also has a point that these questions cannot exist in a vacuum outside of any context, and perhaps it is this context which determines what is considered necessary and contingent and which sets the limits that allow or disallow further questioning in actual discussion.
  • Things That We Accept Without Proof
    One does not have to deny qualia to show their epistemological and semantic uselessness.lll

    :up:
  • Why are things the way they are?
    I think the 'why' is often enough lyrically indeterminate. It's not how but that the world is that fucks us up. Or fucks those up who're in a mood called 'wonder.'lll

    Yes, this is what I was getting at.

    A version that occurs to me is the apparent inescapability of brute fact in any grand narrative.lll

    Right. I think what these type of "why" questions have in common is that they are givens or necessities of our existence. More specifically, they are what is given, axiomatic or necessary for us to be able to ask these questions in the first place (i.e. our having spatiotemporal existence, life, consciousness).

    It's similar to asking: Why is my native language English instead of another language? Or: Why am I me and not someone else? One possible answer might be that it is by virtue of the details of your birth, such as where you were born, who your parents are, who raised you, etc. But I'm not sure that this answer would satisfactorily answer the "why" question.

    Even if we knew all the causes of how the brain produces conscious experiences, this still seems to leave untouched the question of why the brain produces conscious experiences.
  • Why does time move forward?
    C theory, which rejects temporal directionality. — Kuro

    Nobody took this bait.
    I cannot find a difference between B and C. B-theorists define directionality based on entropy levels. If the C-theorist denies this, it seems they are in denial of thermodynamic law.
    noAxioms

    You can download a copy of Matt Farr's paper that @Kuro mentioned here: https://philpapers.org/rec/FARCOT-2. It might help to clarify the distinction between B and C for you.
  • Should hinge propositions be taken as given/factual for a language game to make sense ?
    At the risk of being banned for responding to you, MU:

    The proposition that this is a token is completely irrelevant, and not even taken into consideration when the person retrieves the coat. The person reads the number and gets the coat without considering whether it is a token or not. You could steal someone else's coat by making something which looks like a token, but is a false token, and the attendant would not even notice.Metaphysician Undercover

    Being a token is irrelevant but being a false token is not?

    At some point, in retrospect, one might analyze the action and say something like the idea that this is a token must underlie the attendant's action.Metaphysician Undercover

    It is not the only certainty underlying the attendant’s actions, but one example. There are also the underlying certainties (e.g) that coat checking is a custom, that people own coats, that people have jobs, that there are other people, etc, etc. It’s unthinkable that any of these could be false or doubted. Of course it is imaginable, but not within the confines of our actual lives and what we know of life and society as it is today.

    115. If you tried to doubt everything you would not get as far as doubting anything. The game of doubting itself presupposes certainty.

    232. "We could doubt every single one of these facts, but we could not doubt them all."
    Wouldn't it be more correct to say: "we do not doubt them all”. Our not doubting them all is simply our manner of judging, and therefore of acting.

    It simply represents the mode of analysis, which is to proceed from the particular toward the more general.Metaphysician Undercover

    Nope.

    I’m happy to discuss further if you think that my reading of Wittgenstein is incorrect, but not if you think that Wittgenstein himself is incorrect.

    its supported by a synthesis of all sorts of different ideas and associations which for some reason seem relevant to the person in the situation.Metaphysician Undercover

    This is not inconsistent with what Wittgenstein says except that many of these certainties are shared and are not purely subjective.
  • Should hinge propositions be taken as given/factual for a language game to make sense ?
    I found the following example helpful in coming to understand the meaning of a hinge certainty, so I thought it might be helpful to others here:

    ...if I were to say to the cloakroom attendant as I hand him my token: ‘This is a token’, he would look at me nonplussed. That is not information for him, so why am I saying it? Nothing warrants my saying it. The information he requires in order to retrieve my coat is not that this is a token, but what the number on the token is. That this is a token is the ineffable hinge upon which his looking for the number on the token revolves. Our shared certainty that ‘this is a token’ can only show itself in our normal transaction with the token; it cannot qua certainty be meaningfully said. To say a hinge in an ordinary context is to suggest that it does not go without saying, that it needs support, grounding, context. To say a hinge within the language-game invariably arrests the game, produces a caesura, a hiatus in the game. Conversely, think of the fluidity of the game poised on its invisible hinges: I hand the attendant my token, he glances at the number on it and fetches my coat. Our foundational certainty is operative only in action, not in words. This is well conveyed by Wittgenstein’s image of a certainty which is like a taking hold or a grasp:

    It is just like directly taking hold of something, as I take hold of my towel without having doubts. (OC 510)

    And yet this direct taking-hold corresponds to a sureness, not to a knowing. (OC 511)
    — Daniele Moyal-Sharrock, Understanding Wittgenstein's On Certainty

    Moyal-Sharrock identifies this "sureness" with what Wittgenstein refers to as "objective certainty" (OC 194) (aka hinges), which Wittgenstein says is/are categorically different from knowledge (OC 308).
  • Should hinge propositions be taken as given/factual for a language game to make sense ?
    We learn the meaning of "2" and "3" by counting, saying the name for the number that comes next. Correcting them when they get it wrong.Fooloso4

    But this is not really counting; it is teaching someone to count. Just like saying “this is red” to someone while exhibiting a red patch is, in many cases, not really using language in a language game, but teaching someone how to use the word “red”. Wittgenstein provides several examples in OC where stating rules like “this is a hand” in the course of an actual language game arrests the game, and why people might think you insane to say such things.

    Nature does not teach us to call this “red”, this “a hand”, or this many “2”; these are arbitrary conventions.
  • Should hinge propositions be taken as given/factual for a language game to make sense ?
    I think you have it backwards. One needs to learn the rule first, and the meanings of the terms (“1”, “2”), before they can actually count anything. Just as one needs to learn how to use a word before they can (meaningfully) use it in a language game, or to learn how the pieces move before one can play chess.