In a recent answer to a post, @Ted Wrigley posited that a belief [his own] that is not necessarily true, is not “knowledge in the exacting sense of the term.” (last paragraph of this answer) An astoundingly high criterial bar. Does this mean that in order for a belief or proposition to constitute knowledge [“in the exacting sense”] it must be necessarily true; that only tautologies and logical truths constitute knowledge, again, “in the exacting sense.” (As well, one would assume, as Kant's synthetic a priori and Wittgenstein's hinges/normative "rules," to the extent they can be considered to be truth evaluable.)

How can this be squared with Quine’s observation that it is simply wrong to assume that there is a class of statements which are in principle “immune from revision” in light of experience – that is, that are necessarily true. Because only non-existent necessary truths constitute knowledge [in the exacting sense], is it any wonder that we are inextricably ensconced in what has come to be known as a “post-truth” world?

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    A belief never constitutes (certain or true) knowledge. This is why it's called a belief. When you are in pain you do not say 'I believe I am in pain'. You know you are, even though it is not a necessary truth. Even (what seems to be) a tautological truth might be be false if your calculations contain errors. .
    – user20253
    Mar 15, 2020 at 10:52
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    @PeterJ "A belief never constitutes [true] knowledge." Really? A belief or opinion is simply a judgment that results from evaluation, is it not? How old do you believe you are as of today? Where do you believe California is? Pakistan? Who is the president of the USA? In 1961? Your/a belief (on 3/15/20, or today, another belief [that today is 3/15/20] BTW) that Trump is the president is true, whereas your belief (today) that Obama is the president is false. Nevertheless, the claim you make goes to the heart of my [clumsily articulated] query.
    – gonzo
    Mar 15, 2020 at 18:36
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    Assuming you have in mind the traditional theory of knowledge, no. A belief only needs to be actually true (in this world), not necessarily true (in every possible world) to be knowledge, nor do we need to know whether it is true or not to make it knowledge. Quine’s point is not even relevant here, whether something is true or necessarily true has little to do with whether it is immune from revision. We can, in principle, justifiably believe something true, and hence know it, and then (mistakenly, but also justifiably) revise it, and cease to know it.
    – Conifold
    Mar 15, 2020 at 19:41
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    I think he is using it colloquially for rhetorical emphasis, whereas your references to tautologies and logical truths suggest a different meaning.
    – Conifold
    Mar 15, 2020 at 22:45
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    @gonzo: I only meant 'calling out' in the literal sense of referencing (need to be more careful of my language). nothing untoward was implied. And then I deleted that comment anyway and added a link to it myself. it's all good. 😀 Mar 17, 2020 at 18:10

6 Answers 6


As I see it — and keeping in the Wittgensteinian vein — The difficulty we have here is that the term 'knowledge' is vaguely defined across a number of language games, and it's rarely clear which language game we're playing when we invoke it. That causes confusion.

So allow me to go ahead and deconstruct this topic, to see where we end up. When we talk about 'knowledge,' we generally want knowledge to express 'truth.' This is the rationale behind the 'justified true beliefs' paradigm. But 'truth' is a problematic concept. 'Truth' (with a capital 'T', meaning the strongest version of the concept) is something close to a Platonic form: universal, a-temporal, irrevocable, and irreducible. 'Truth' in this abstract sense is a matter of metaphysics that we have no direct access to. We can presume that the Truth 'is out there' with proper X-Files sensibilities, but we will inevitably Mulder and Scully ourselves trying to get a handle on it.

For example, if I claim that the following statement is 'True':


What I mean is that in any time, place, or context — e.g., the modern US, ancient China, 25th century France, even on an alien planet in a different universe — if we have one of something and a different one of something, and we put them together, we will have a two somethings. But then, of course, I have to realize that while this equation may always be 'True' within the mathematical domain of arithmetic, not everything in the universe is subject to the rules of arithmetic. For instance, if we have one container of water and another container of water and we pour them together, we still only have one container of water (now containing twice the volume). If we have one apple and one orange and we put them together, we do not have two of anything (unless I switch conceptual frames and start talking about fruit).

The point here isn't to quibble with the nature of arithmetic; the point is that 'Truths' are generally only 'true' within bounded domains. We can say that 1+1=2 is a 'truth' so long as we understand that it is true for a particular type of thing: countable, indivisible, immutable objects of a uniform type. If we understand the boundaries, then we can say the claim is 'true', and we have something we can call 'knowledge.'

This is the case even for ridiculous claims. For instance, if I say:

"Purple-striped unicorns are superior to pink-speckled unicorns"

no one would dignify calling that 'knowledge' unless there were a particular context — say a board game or child's TV show — which provides boundaries for that claim. If there's (say) a children's TV show called 'Ultimate Unicorns' in which the purple-striped unicorn shoots a laser out of its horn while the pink-speckled unicorn sneezes up healing mucus, then my claim has truth-value within that context, and we can have a fiery, meaningful debate about whether lasers are 'superior' to healing mucus.

But notice how the nature of 'truth' has changed here. Truth is no longer 'universal, a-temporal, irrevocable, and irreducible' but exists only within a frame of reference (be it arithmetic objects or a particular TV show). And these particular frames of reference happen to be well-delimited. I can specify which objects are subject to arithmetic and which are not; I can specify that we are speaking about a particular show. Can we do the same for other contexts? Can we specify the boundary conditions for physics, climate science, ethics, aesthetics? Even physics clearly stops working at certain point — event horizons, the beginning of the universe, at the quantum level — but the exact boundaries of applicability are still something of a mystery.

Without precise conceptual boundaries, the notion of 'truth' starts to fall apart. Either we make the leap and assert a Platonic ideal of 'Truth,' or we are forced back to mere justified belief.

So now if we can go back to the main point, we can tease apart knowledge and truth, seeing that 'knowledge' has at best an asymptotic relationship to metaphysical 'Truth'. Then we no longer have to use 'knowledge' in the exacting sense of the term — meaning we no longer have to make Platonic assumptions — and merely need to recognize the relationship between claims and boundary conditions that produces practical knowledge.

  • Once again, you 'knocked it out of the park.' Your answer reminded me of a much beloved book I read many years ago: Michael P. Lynch's Truth in Context, where he discusses pluralism as the notion that there are incompatible but equally acceptable accounts of some subject matter. He describes the issue I pose in what I called [in comments] my "embedded question" as that of finding room for objectivity in pluralism, that is "allowing for different truths without slipping into the nihilistic position that there is no truth at all." The "slippery slope" from pluralism into into nihilism.
    – gonzo
    Mar 19, 2020 at 19:13
  • Both of you will end your lives as dead lifeless bodies. That is truth with a capital 'T'. It conforms to all of the conditions mentioned in your question; it is knowledge, it is metaphysical, (real), and it is absolutely irrevocable. As for belief, belief is a purely subjective conjecture and it's status as knowledge hinges on whether you can learn something from your belief. Even if it's false or untrue one often learns the most from mistaken beliefs.
    – user37981
    Oct 11, 2020 at 4:40
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    @CharlesMSaunders: We will end our lives as dead, lifeless bodies within the context of of a loosely secular-scientific worldview. Buddhists, Christians, Jains, Jews, Muslims, Christians, etc. would beg to differ (their own respective worldviews having a somewhat different context). You haven't challenged what I've said; you've exemplified it. Prove that people do not continue on after their bodies die, or accept that your 'knowledge' is only tangential. Knowledge is like a peach: fuzzy on the outside and squishy on the inside, but good just as it is. Oct 11, 2020 at 5:52
  • @CharlesMSaunders Saying that belief is necessarily a purely subjective conjecture goes against everything in analytical epistemology. The "True" proposition that you put forward as an example appears to be one of your beliefs. Oct 11, 2020 at 15:30
  • @Ted Wrigley First you said truth is universal and then you also claimed that it is trans-universal :) Oct 11, 2020 at 16:32

This is an excellent question gonzo, and it highlights a major problem in contemporary philosophy. Supporting Ted Wrigley, is the SEP entry on knowledge, which agrees with him: https://plato.stanford.edu/entries/knowledge-analysis/#TrutCond

1.1 The Truth Condition

Most epistemologists have found it overwhelmingly plausible that what is false cannot be known. For example, Hillary Clinton did not win the 2016 US Presidential election. Consequently, nobody knows that Hillary Clinton won the election. One can only know things that are true.

However, as you note, pretty much everything we "know", including the existence of the physical world, other minds, and logic proofs, WE COULD BE WRONG ABOUT! Hence, since we can't know "truth", this standard for knowledge appears to be a null set.

Pragmatically, basically everybody treats "very well supported" as good enough to approximate truth. But as you point out, this is abandoning actual "truth" as a standard for knowledge.

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    Of course we could be wrong about those things. No epistemologist denies this, and that doesn't contradict the truth condition.
    – E...
    Mar 15, 2020 at 18:41
  • If "is true" is a necessary requirement for knowledge, and we can never know if "is true" is actually the case, then we cannot ever know if we have any knowledge. The alternative, which pretty much everyone accepts outside the SEP and most philosophy discussions is that "sufficiently well justified" is all that is needed for knowledge, and "is true" is not necessary.
    – Dcleve
    Mar 15, 2020 at 18:45
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    If you know something, then you know that it is true. So there's no problem there. Whether you know that you know is a different matter, but why should that be a problem?
    – E...
    Mar 15, 2020 at 18:49
  • So -- what do you mean when you say you know something? Or do you think there is no valid way to use the word because the requirement is too extreme, so you never say you know anything?
    – Dcleve
    Mar 15, 2020 at 18:53
  • No, I am not saying that. What do I mean by saying that I know something? I mean that I know it. Not everything has to be given a reductive definition.
    – E...
    Mar 15, 2020 at 18:55

Maybe first we might apply a certain amount of charity in our interpretation of Ted’s statement?

The binding of the “don’t necessarily” in your quote strikes me as looser than I think you’re taking it. A charitable reading would say that Ted is suggesting that “false beliefs fail to count as knowledge, and this might be the case of some things that would otherwise count if they were true”, as opposed to “beliefs that might be false fail to count as knowledge in all circumstances, even if they contingently are true”.

The latter seems, as you say, too strict a requirement on knowledge in the face of uncertainty. The former, though, seems reasonable - false beliefs aren’t knowledge, even if believing them can be reasonably justified. Nobody can ever know that Nick Clegg was the British Prime Minister, even if we might tell some story about how they could quite honestly and genuinely have come to that conclusion.


The classical definition of knowledge, going back to Plato, is "justified, true belief." Some of the typical attacks on this revolve around what is "justified", what is "true" and what is "belief."

In this case, I think there may be some ambiguity as to what is meant by "necessarily true." Do we mean a "necessary truth," something which cannot be other than true? Not all philosophers believe these exist, and I'm not personally aware of any that argue that only necessary truths can undergird knowledge. Or do we mean that its truthfulness is "necessary" to it being considered knowledge? That much is entailed by the classical definition.

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    If the best we can ever know the "truth" is just a well justified belief, then what is the value of adding "true" to "justified belief" as a criteria for knowledge? I think this is the central question being asked. If "certainly true" rather than "well, it is probably true" is needed for knowledge, the only items that seem to satisfy that are logical necessities.
    – Dcleve
    Mar 17, 2020 at 21:21
  • @Dcleve The added value is in providing an ontogically stronger definition. But epistemically and pragmatically there is no difference. Oct 11, 2020 at 1:45
  • @Dcleve No, there could be tons of truths that we know appart from logical necessities. It is not required that we can definitively prove them true. All that is required is that they be true. Oct 11, 2020 at 15:32
  • @ChrisSunamisupportsMonica What philosophers don't believe in necessary truths? Why? Oct 11, 2020 at 17:10
  • You can have a justified belief that turns out to be false. I checked the bus time table, and called the bus company, and as the result I have the justified belief that the bus will leave at 8:05. But the bus has an accident and my justified belief is wrong. People get convicted because there is a justified belief they are guilty (guilty beyond reasonable doubt), and that justified belief is sometimes wrong.
    – gnasher729
    Oct 11, 2020 at 19:02

If you are talking about factive knowledge, yes. If not, no.

Factive knowledge is by definition knowledge that has to be true in order for it to be knowledge. "Factive" is simply the type of knowledge such that, if someone knows that p, then p (of course if p is true, then p is truth-apt). The traditional Platonic definition of knowledge is as factive knowledge.

Non factive knowledge can be knowledge without being true, for example the scientific knowledge of Newton is called so, even though his theory was false and has been superseded.

This is just a matter of definition. This is just to have two concepts of knowledge, so that we can say that Newton had scientific knowledge without commiting to deem it true (Newton's knowledge of Newtonian mechanics was non-factive knowledge).

An example of factive knowledge is the knowledge that 2+2=4. We can confidently say that it's factive knowledge because we see no way in which it could be false. Although, if it turns out that it is false, then we would know that it was non-factive knowledge all along.

I suppose these definitions can be used with any theory of truth.

What entitles the believer to claim that their belief is true (besides the evidence) is the need to avoid pragmatic contradiction. It would be a pragmatic contradiction to claim "p" and to claim at the same time: "I don't know that p is true" (see Van Fraassen for the concept of pragmatic contradiction). It is not Newton who is saying that his knowledge was only non-factive, it is us saying it.

But in your question I believe you are mixing two completely different things: i) the necessity of a proposition being true in order for it to be known, and ii) the necessity of it being necessary.

If it is true that my mom's name is Jane, then its knowledge is factive knowledge. But of course my mom could have been named something else.

  • Can you add details and examples to your post? Oct 11, 2020 at 0:32
  • @Mark Andrews Done. Oct 11, 2020 at 0:38
  • Some examples of "factive knowledge," perhaps. Keenly focusing upon the demarcation (critria and boundry between what is and what is not FN] issue. And, a second, but related issue, are we talking 'true" according to the correspondence theory, pragnmatism, what? Verification ala Ayers? Popperian falsifiability? Etc.
    – gonzo
    Oct 11, 2020 at 1:56
  • @gonzo I'm already giving the demarcatory criteria. Added example of FN. Regarding my theory of truth, I'm a correspondentist. Oct 11, 2020 at 2:05
  • @gonzo Popperian falsifiability is not a criterion of truth. Oct 11, 2020 at 2:17

Knowledge is just information, so, not necessarily, just if the belief is false, then the "knowledge" is also false and if we process false knowledge, we will have false results

If you have undoubtable proof then you have "true knowledge", you have truth, otherwise you might have "false knowledge", in case your knowledge is false, does not mean you do not have knowledge at all, you just have knowledge that is not the truth, it might not be the truth, but you still know it, you have that information, but that means you don't know the truth, you know the lie, you still know something related to the subject you examine if your knowledge about it is true or false

  • And no, knowledge is not just info, it has to be believed and justified. Oct 11, 2020 at 15:39

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