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Whenever someone looks at an ambiguous figure, like the duck-rabbit, their perceptions are in such a state of undecidability:

1) Person sees a duck.
2) Person sees a rabbit.
(Google duck rabbit for images)

Imagine a person - Steve, could see only the duck. Imagine a person, Sally, could see only the rabbit. Steve could gain no more information about the hidden rabbit status of the duck, nor could Sally gain information about the hidden duck status of the rabbit. If you compose and conjoin what they know, there is no more attainable evidence. This is because Steve and Sally together have all information about the duck status and the rabbit status of the duck rabbit; evidence is consistent with the duck and the rabbit status, and so no further knowledge of the duck rabbit is attainable. However, if Steve and Sally were invited to look very closely at the duck-rabbit picture they were shown, they may be able to discover certain things they did not know before about how it was drawn. But this is impossible, since no further knowledge of the duck rabbit is attainable!

Where does this go wrong? I'm not completely sure.

For some proposition (statement, claim, postulate), p, if attainable evidence is consistent with both p and ¬p, then further knowledge thereof is unattainable. — jorndoe

What do you mean by this? If I have evidence that there's a cup in my cupboard then this is consistent with the claim that you're man and with the claim that you're not a man. So is further knowledge unattainable?

For some proposition (statement, claim, postulate), p, if attainable evidence is consistent with both p and ¬p, then further knowledge thereof is unattainable. It’s like a difference that makes no difference — not information.
......
What’s up with this stuff anyway? What do you think? — jorndoe

I find it a useful way to think of things. It enables one to work out what controversies there is no point in discussing.

I find ontological debates of that nature. As far as I can see, all ontological claims are differences that make no difference. Yet they generate the greatest controversy and the longest threads on this and on the predecessor forum.

There are two odd ironies here. The first is that I often can't resist getting involved in the ruck of an ontological debate, for the pure intellectual stimulation of it, even though there is absolutely nothing at stake - as far as I can see. It's almost as though the fact that there's nothing at stake is what makes it so delicious to dive into the banter.

And that leads to the other irony. It's what somebody, somewhere, once so perspicaciously said: that the passion invested in philosophical debates is generally in inverse proportion to the importance of what's at stake.

That's only true if we exclude applied ethics though (but not meta-ethics). Ethical debates are important, and do generate great passion. But its arguable that ethics should be classified under politics rather than philosophy. I reckon it's generally in both.

I would guess that Jorn means 'if all attainable evidence is consistent with both, then further knowledge is unattainable'. In that case, we have no evidence that allows us to choose between the proposition and its negation. Evidence that there's a cup in the cupboard doesn't help us distinguish the truth of the proposition that Jorn is a man, but neither does it preclude the possibility that we might have other evidence that does support one or the other - such as that Jorn has a name that is nearly always given to male rather than female babies.

Jorn, please correct me if I've misunderstood you.

I would guess that Jorn means 'if all attainable evidence is consistent with both, then further knowledge is unattainable'. — andrewk

Oh. That's pretty much a truism, isn't it?

For some proposition (statement, claim, postulate), p, if attainable evidence is consistent with both p and ¬p, then further knowledge thereof is unattainable. It’s like a difference that makes no difference — not information. — jorndoe

I'd like to see some evidence of this, just to make sure it's not dismissing itself.

Whenever someone looks at an ambiguous figure, like the duck-rabbit, their perceptions are in such a state of undecidability:

1) Person sees a duck.
2) Person sees a rabbit.
(Google duck rabbit for images)

Imagine a person - Steve, could see only the duck. Imagine a person, Sally, could see only the rabbit. Steve could gain no more information about the hidden rabbit status of the duck, nor could Sally gain information about the hidden duck status of the rabbit. If you compose and conjoin what they know, there is no more attainable evidence. This is because Steve and Sally together have all information about the duck status and the rabbit status of the duck rabbit; evidence is consistent with the duck and the rabbit status, and so no further knowledge of the duck rabbit is attainable. However, if Steve and Sally were invited to look very closely at the duck-rabbit picture they were shown, they may be able to discover certain things they did not know before about how it was drawn. But this is impossible, since no further knowledge of the duck rabbit is attainable!

Where does this go wrong? I'm not completely sure. — fdrake

i suspect your example conflates the notion of data with the notion of evidence that is only meaningful with respect to a rule of interpretation.

Assuming Sally and Steve both see an identical image, it does not follow that they would interpret the image in the same way, unless they additionally share identical rules of judgement for identifying ducks and rabbits. And even then, they might still differ in their judgements if they each possessed different perceptual objectives, each seeing only what they wanted to see.

I'm not sure what you mean, regardless have some words.

Assuming Sally and Steve both see an identical image, it does not follow that they would interpret the image in the same way, unless they additionally share identical rules of judgement for identifying ducks and rabbits. And even then, they might still differ in their judgements if they each possessed different perceptual objectives, each seeing only what they wanted to see.

Let's refine it a little bit. Steve and Sally are asked to determine whether the image is of a duck or a rabbit. Assume Steve can only see the rabbit, whereas Sally can only see the duck. The domain of propositions that they're being asked to find evidence in is something like:

A ={those properties of the image which make it look like a duck}
B={those properties of the image which make it look like a rabbit}

however, each duck property of the image resembles a rabbit property, seen from a different view.
I believe the rules of judgement that they follow correspond to whether they see the duck or the rabbit. So Steve is following rabbit-highlighting-rules and and Sally is following duck-highlighting rules.

So A=B, since each duck-highlighting-rule is also a rabbit-highlighting-rule. But when the image is seen as a duck, it is not seen as a rabbit. There are only two relevant interpretations of the image for the question: 'the image is of a rabbit' and 'the image is of a duck', supported by A and B respectively. But since A and B are the same, we cannot learn anything about whether the image is a rabbit or a duck.

agreed!

However, if Steve and Sally were invited to look very closely at the duck-rabbit picture they were shown, they may be able to discover certain things they did not know before about how it was drawn. But this is impossible, since no further knowledge of the duck rabbit is attainable! — fdrake

If there are no contextual reasons to classify the duck-rabbit as one thing or another, and if it is also assumed that noticing any additional data features doesn't influence judgement, then no further knowledge of the duck-rabbit is attainable.

So what's the problem?

@sime

Change the thought experiment so that a person who's never seen it before and isn't compelled by the assumptions to see only a duck or only a rabbit. Assume they see the duck first, but then they see the rabbit. They will have learned something, namely that the picture can be seen as a duck or a rabbit, but there is no fact about the image which will allow them to distinguish duck from rabbit. If they've learned something, and it's not a fact about the image, what is it?

Change the thought experiment so that a person who's never seen it before and isn't compelled by the assumptions to see only a duck or only a rabbit. Assume they see the duck first, but then they see the rabbit. They will have learned something, namely that the picture can be seen as a duck or a rabbit, but there is no fact about the image which will allow them to distinguish duck from rabbit. If they've learned something, and it's not a fact about the image, what is it? — fdrake

their perceptual response to the image :)

A form of irreducible knowledge subsuming both the subject and object.

But of course, the fact that perception is active does not in general imply that identical data is being judged - at least if by identical data one includes additional contextual information that that the observer surreptitiously obtains or creates during the course of judgement.

For example, in the case of the spinning ballerina illusion one's eye might wriggle in a certain motion to bias perception towards one interpretation.

Agreed

Is it irrelevant that the duck-rabbit has been heavily "abstracted"? That is, many, many details of ducks and rabbits are left out, aren't they? And we know the method: only those features are retained that can be made ambiguous as features of either a duck or a rabbit. The remaining features are even distorted a bit off true to push them more toward an "average" feature. (That we accept this distortion is really interesting.)

So I would think what's learned is something about abstraction.

For some proposition (statement, claim, postulate), p, if attainable evidence is consistent with both p and ¬p, then further knowledge thereof is unattainable. It’s like a difference that makes no difference — not information. — jorndoe

Does this class encompass all statements about the future?

(sorry for my absence; the thread was intended for general discussion in any case)

There are a few kinds of propositions.

p = all swans are white
might once have been thought true, until black swans were found. Known evidence was consistent with p, yet anyone might have claimed ¬p without deriving a contradiction. p at least seemed truth-apt, however useless the claim may seem.

Sagan's garage dragon is another kind of claim, or at least further evidence-immune. It seems impossible to differentiate whether the existential claim is true or false. Perhaps it's possible to discover a means by which to find the dragon, or lure it to make it's presence known? :) (Neutrinos, first found in 1955 by Cowan and Reines, can be rather difficult to deal with.)

p = there's an invisible spirit/ghost that keeps an eye on you at all times
could be further along this path. Can't think of any evidence that specifically differentiates p and ¬p.

I guess there's broad agreement that solipsism isn't particularly dis/provable (in a purely deductive sense). Or take whatever other incompatible -isms you fancy, doesn't matter in this context.

It's trivial to immunize claims (as alluded to by Sagan). At what point do such claims become differences that make no difference (if they do)?

I'd been thinking along similar lines. To learn something isn't to learn something in a vacuum, it's to learn within a context. So in terms of the pictures, nothing new would be learned (if that thought experiment is valid); but in terms of knowledge about the duck-rules and the rabbit-rules, we could.

What’s up with this stuff anyway? What do you think? — jorndoe

I've developed a principle, Clark's Razor, which is useful when I am working on a design. Here's how it goes - If there are two designs that are equal in terms of cost, effectiveness, permitting, and any other way that can be determined, pick the one that's easier to draw. That highlights that the only times these types of rules really matter are when decisions which have consequences have to be made. They don't really have anything to do with truth, they have to do with what to do next.

That highlights that the only times these types of rules really matter are when decisions which have consequences have to be made. They don't really have anything to do with truth, they have to do with what to do next. — T Clark

This is really nice.

Generalize it and reword the second sentence, and you've reinvented pragmatism!

When I asked about statements about the future, I was thinking about an ambiguity in the word "attainable". For instance, it could be that everything we could possibly know is consistent with rolling a 1 and with rolling a 6. But that doesn't mean I can't find out which one I roll by just going ahead and rolling the die.