The standard, common sense understanding. — Michael

I don't think philosophy is done that way. We can't/shouldn't employ substandard definitions. We need clear-cut concepts.

You should read Philosophical Investigations.

It's better to let go of this constraint and simply use the word knowledge as we tend to do in ordinary life, which usually does not pose much problems in discussion, outside of specific cases like this. — Manuel

The thing is that ordinary use varies, and there is a sense of knowledge that answers the JTB criteria. The truth criterion is justified by locutions such as "I thought I knew that P, but I was wrong" (i.e. I didn't actually know that P). Or "A thinks that she knows that P, but she is mistaken."

But I agree that JTB picks out at best some, but not all ordinary senses of knowledge.

You should read Philosophical Investigations. — Michael

I hope to but not anytime soon.

By the way, IF the JTB definition is going to be tinkered around with in the way you describe, sure you're on target.

:flower:

The thing is that ordinary use varies, and there is a sense of knowledge that answers the JTB criteria. The truth criterion is justified by locutions such as "I thought I knew that P, but I was wrong" (i.e. I didn't actually know that P). Or "A thinks that she knows that P, but she is mistaken." — SophistiCat

Sure. As is the case for most words.

But I agree that JTB picks out at best some, but not all ordinary senses of knowledge. — SophistiCat

Yup.

I don't see the benefit of saying knowledge must be JTB.

"The visual data is believed to be consistent with the existence of a cow, relative to the present state of the observer that summarises the reliability of unstated contextual assumptions".

Shouldn't sentence A be considered an acceptable expression of justified true belief?

I think so, even if the impossibility of error is implied.

JTB is posited not as a dictionary definition of the word 'knowledge' but as a specialist philosophical definition. Like you though, I am not sure how useful it is for that purpose. Sometimes it seems that it has no other use than for people to argue over it, but perhaps my perception is skewed by these perennial Gettier-type debates on the internet.

Update

You're a farmer.

Scenario 1: You see what looks like a cow (it's a cloth waving in the breeze). You say to yourself "there's a cow in my field."

Scenario 2: You see an actual cow and you conclude "there's a cow in my field."

Gettier fails to account for the difference between "what looks like a cow" and "an actual cow".

Gettier is mistaken in thinking he has found a failure in our understanding of knowledge. He has discovered fallibility. — unenlightened

:up:

↪TheMadFool You should read Philosophical Investigations — Michael

:up: :up: (I've recommended TMF do so but he seems incorrigibly stubborn when it comes to Witty.)

Intriguingly, Martin Rees claims that Newton's laws are physically hardwired in our brains. How else do we make good estimates on what we can handle, physically, and what we can't. — TheMadFool

Martin Rees is wrong (or just joking). "We make good estimates ..." far more often parochially with ad hoc heuristics (i.e. trial and error correlations) than we do generally with algorithmic calculi (i.e. soundly inferred causal relationships), the latter of which "Newton's laws" – physical laws being nothing more than invariant properties of fallible (defeasible) theoretical models which explain physical regularities – consist.

If a calculator tells me that the answer to 123 × 123 = 15,129 then I am justified in believing that 123 × 123 = 15,129. — Michael

Except in the case where the calculator is broken, or has been tampered with or ... In such cases, your justification dissolves. I am saying that just as one can believe one knows X when in fact one does not (and cannot) because X is false, so one can believe one is justified by X in believing Z when one is not, because X is false. Particularly in the case where Z = "I know that X ".

one can believe one is justified by X in believing Z when one is not, because X is false. — unenlightened

We can be justified in believing things even if our belief or its evidence is false. If I’m a bartender and someone shows me a fake ID that I believe to be real then I am justified in believing that they are 18 and so that I am allowed to sell them alcohol. That’s why I wouldn’t be charged with selling alcohol to someone underage.

Thankfully the legal system uses this common sense understanding of justification and not the sense that you and TheMadFool seem to use.

I am justified in believing that they are 18 and so that I am allowed to sell them alcohol. — Michael

Indeed. Nobody will blame you, just until you learn that they are not 18 and you are not allowed to sell them alcohol. You will claim to know that they are 18, and you will be wrong, but justified in thinking you are right. You are confusing what is a reasonable justification with what is a true justification. As soon as it is pointed out that the passport he showed you is issued by the government of Narnia, you are no longer justified in your belief. and you will become responsible. Indeed perhaps you are already at fault for not noticing such a feeble attempt at a fake id. This too is common sense.

You will claim to know that they are 18, and you will be wrong, but justified in thinking you are right. — unenlightened

And in the Gettier case they are 18. They bought the fake ID when they were 17 and haven't yet replaced it with a real one. So I have a justified true belief that isn't knowledge.

You are confusing what is a reasonable justification with what is a true justification.

I'm not confusing the two. The justified true belief account of knowledge doesn't distinguish between different kinds of justification. It simply argues that we have knowledge if we have a justified true belief. The above example is an example of a justified true belief that isn't knowledge, and so the justified true belief account of knowledge isn't correct.

Gettier cases showed that we need something else; a JTB+G account of knowledge, where "G" is some fourth condition, which in your case is that the justification is a "true" justification.

which in your case is that the justification is a "true" justification. — Michael

There. that wasn't so hard was it?

Martin Rees is wrong (or just joking). "We make good estimates ..." far more often parochiallly with ad hoc heuristics (i.e. trial and error correlations) than we do generally with algorithmic calculi (i.e. soundly inferred causal relationships), the latter of which "Newton's laws" – physical laws being nothing more than invariant properties of fallible (defeasible) theoretical models which explain physical regularities – consist. — 180 Proof

How does a robotic hand catch thrown objects? My hunch is it uses Newtonian mechanics, the formulae therein, to do a superfast calculation of an object's trajectory.

How does a human catch a ball or other object thrown at him/her?

This issue has deeper significance - the same function being accomplished using two different methods (the easy way - humans - and the hard way - robots).

Not having put out milk last full moon doesn't justify a belief that fairies exist and cursed his cabbages.

Whereas seeing something that looks like a cow in his field may justify his belief that there is a cow in his field. — Michael

To one subscribing to internalism, a justification is valid if one's internal subjective reasons are considered sufficient to hold to a belief.

To one subscribing to externalism, a justification is valid only if there are external facts considered sufficient to hold to a belief.

As to your first statement, I would hold that justification invalid to an internalist. It is incoherent. As to the second statement, the justification is valid to an externalist.

All you never wanted to know on the subject: https://iep.utm.edu/int-ext/

"S knows P" is the disputed propositional form. The trouble with this piece of silliness is that the integrity of 'P' is simply an assumption. There is no P simpliciter, for you cannot separate P from the justification of knowing P. Every time you try (consider the history here of severed head and barn facsimile attempts) you run into the impossibility of establishing P at all! I mean, before you talk about what it is to know P, you have to first establish P independently of the conditions for knowing P, but this is impossible because P's affirmation IS an epistemic assumption to begin with!!!!
They wasted so much time on this piece of rubbish. It just goes to show you what a waste of time analytic philosophy has become.

P = Aliens exist.

There's a proposition but I don't know if P or ~P because I don't have proof (justification).

If the cowishly shaped cloth is a cow then there is a cow in my field, therefore if I can infer that the cowishly shaped cloth is a cow given the evidence then I can infer that there is a cow in my field given the evidence. — Michael

I'm with TMF; in this example there is no problem for JTB. The belief that there is a cow on his field is not specific enough. It's a fudge; what the farmer actually believes is that there is a cow in his field at the location of the cow-shaped cloth, so his belief, adequately specified, is false.

:ok:

Violation of what I call the proportio divina rule: The conclusion is not proportionate to the premises.

Correct conclusion: That (the waving cloth) is the cow in my field (only one specific location possible)

Incorrect conclusion: There is a cow in my field (It could be anywhere in my field - multiple locations possible).

in this example — Janus

Any examples that cause problems for the JTB theory of knowledge?

How does a human catch a ball or other object thrown at him/her? — TheMadFool

As I said:

"We make good estimates ..." far more often parochially with ad hoc heuristics (i.e. trial and error correlations) ... — 180 Proof

If JTB supports a claim about reality then it is a poor definition of knowledge? Is that why people are arguing here?

Given that our understanding of reality is incomplete we are not exactly able to know everything so there are necessarily beliefs we have now that we say are justified true beliefs but reality does not hold up to them - we’re just ignorant.

We only have irrefutable knowledge when we set limits and rules (in abstraction like mathematics). Errors can still lead to false claim of knowledge though.

The whole point of Gettier is to point out that people can get the right answers for the wrong reasons. Giving a correct answer does not mean you hold knowledge about the subject the question was framed in.

Why is this so hard for some of you to grasp? Did I miss something?

Can't think of any offhand: I've never been that interested in Gettier problems.

Why is this so hard for some of you to grasp? Did I miss something? — I like sushi

The idea of JTB really is not concerned with whether we know anything or don't know anything; it's just a definition of knowledge. We may have true beliefs, but they don't count as knowledge unless we have good reason to hold those beliefs.

it's just a definition of knowledge. — Janus

It is a poor one if many people view it differently though, right?

There is considerable disagreement among epistemologists concerning what the relevant sort of justification here consists in.

It is worth noting that one might distinguish between two importantly different notions of justification, standardly referred to as “propositional justification” and “doxastic justification”.

The precise relation between propositional and doxastic justification is subject to controversy, but it is uncontroversial that the two notions can come apart.

Something’s truth does not require that anyone can know or prove that it is true.

Knowledge is a kind of relationship with the truth—to know something is to have a certain kind of access to a fact.

The belief condition is only slightly more controversial than the truth condition. The general idea behind the belief condition is that you can only know what you believe. Failing to believe something precludes knowing it.

https://plato.stanford.edu/entries/knowledge-analysis/#KnowJustTrueBeli

If JTB says that Flatearthers are justified in their belief and that their belief in the Earth being a disc rather than a spherical object is 'knowledge' then knowledge looks to be pretty useless. If someone says they have some knowledge about something why should I take them seriously?

JTB may as well say that everything we experience is 'knowledge'. Well, so what?

I have a definition equally as good. Anything anyone pays any attention to they have knowledge of. Nothing to do with truth or justification needed. We recognise something and question it in some manner. That is where knowledge is born.

Breathing is not something I usually have any knowledge of unless I am directly paying attention to it, questioning it and/or studying it. Generally speaking though my day-to-day life is not taken up by holding knowledge of breathing up for conscious scrutiny. If you keep following this definition of knowledge compared to JTB it has more legs.

I'm with TMF; in this example there is no problem for JTB. The belief that there is a cow on his field is not specific enough. It's a fudge; what the farmer actually believes is that there is a cow in his field at the location of the cow-shaped cloth, so his belief, adequately specified, is false. — Janus

If one can infer B from A and if B entails C then one can infer C from A.

Take the example of the bartender given the fake ID. His belief that the ID is real is false, but his derived belief that the person is 18 is true.

I think there point is that the bartender is Justified to Believe this as True because the document is convincing enough and the age of the person questionable enough to warrant their position as 'correct'.

That the person's age is under 18 in reality seems to be of little concern to the definition of knowledge - knowledge can be faulty.

That is the only way I can make sense of what they are saying here.

That the person's age is under 18 in reality seems to be of little concern to the definition of knowledge - knowledge can be faulty. — I like sushi

Knowledge is being defined as justified true belief, not just as justified belief.