Three stages

[jeremyp]

NS,

But that the “with my current state of knowledge” is the critical a priori point here. I have no basis to assume that my current state of knowledge gives me anywhere near enough information to rule out anything – square circles and "y*&^%(^TO*G" included. The former is impossible only inasmuch as my grasp of logic tells me it is, and the latter may turn out to have meaning even though I have no way of discerning what it is.

Absent omniscience, on what ground then could argue that either of them (or anything else) isn’t possible?     

But if I cannot say that anything is impossible, aren’t I also saying necessarily that anything is therefore possible (even if that “thing” is incoherent to me)?

You can definitely rule out square circles. That is definitionally an absurdity.

The problem is that NS is sort of conflating two things. There are two questions

A does x exist?

B is it possible that x exists?

If we answer B with "yes" it tells us nothing about the answer to A. If we answer B with "no" we are also answering A, so it follows the same standard of evidence is required.

I can't definitively rule out an afterlife, so I have to concede one is possible.

[jeremyp]

So the reverse of that is simply personal credulity, and equally worthless.

No. The reverse of "I can't believe it so it must be true" would be "I could believe it therefore it must be true", which is obviously a fallacy and so is the weaker "I could believe it therefore, it could be true". My position is "I can't rule it out therefore I must concede it might be true".

[Nearly Sane]

You can definitely rule out square circles. That is definitionally an absurdity.

The problem is that NS is sort of conflating two things. There are two questions

A does x exist?

B is it possible that x exists?

If we answer B with "yes" it tells us nothing about the answer to A. If we answer B with "no" we are also answering A, so it follows the same standard of evidence is required.

I can't definitively rule out an afterlife, so I have to concede one is possible.

No, I'm not conflating those 2 questions. In order to say something is possible - a claim to knowledge, you  need sufficient knowledge to say that it is.

[Nearly Sane]

No. The reverse of "I can't believe it so it must be true" would be "I could believe it therefore it must be true", which is obviously a fallacy and so is the weaker "I could believe it therefore, it could be true". My position is "I can't rule it out therefore I must concede it might be true".

The statement that 'it might be true' is not equivalent to 'it is possible'.

[jeremyp]

No, I'm not conflating those 2 questions. In order to say something is possible - a claim to knowledge, you  need sufficient knowledge to say that it is.

I have sufficient knowledge to say that it is possible.

[Udayana]

But to say something is "not impossible" surely leaves open the option of it being "possible".

If the "not impossible" is a proposal that is grounded on what is currently in place: say that the storage potential of batteries for electric cars could be increased by 20% over the next 5 years due to technical advances, then that proposal is "not impossible" since it is informed speculation based on what is extant, even if it turned out to be wrong.

However if "not impossible" is the response to a claim like 'an after life' that has no grounding in logic, reason or credible evidence then surely the correct response is say that without any grounding in logic, reason or credible evidence then the claim is currently no more than meaningless white noise, and that no assessment of it's 'possibility' can therefore be made. In essence, the 'impossible/possible' categorisation can't even be considered since it can't apply as things stand.

Spot on, Gordon.

Ascribing truth values or probabilities to meaningless propositions is not valid - if allowed just drags in the "principle of explosion" where no statement has any useable meaning.

I'm just surprised by how a Sriram OP (essentially drivel) can still cascade into a flow of so many bad arguments.

Still ... "if 6 turned out be 9 ... " 

[bluehillside Retd.]

NS,

I'm confused by your last paragraph. Prof D is saying that because we can't say 'after life' is impossible, therefore it is possible. And yet you've agreed with me saying 'Saying something is possible is ruling out that it is impossible'. So that would mean you think Prof D has a logical paradox in his position.

Maybe I’m having a slow start this morning, but I can’t see the paradox. If we can’t say that anything is impossible (and I think we can’t no matter how undefined, apparently contradictory or incoherent to us) then it’s necessarily possible isn’t it?   

[bluehillside Retd.]

Jeremy,

You can definitely rule out square circles. That is definitionally an absurdity.

Insofar as our grasp of logic makes it an absurdity that's true, but how would you know that that logic is universally applicable? How for example would you rule out "you" being a computer avatar that's just programmed to to think square circles are absurdities?   

[BeRational]

You can definitely rule out square circles. That is definitionally an absurdity.

The problem is that NS is sort of conflating two things. There are two questions

A does x exist?

B is it possible that x exists?

If we answer B with "yes" it tells us nothing about the answer to A. If we answer B with "no" we are also answering A, so it follows the same standard of evidence is required.

I can't definitively rule out an afterlife, so I have to concede one is possible.

Using a silly example. If there was a murder in the manor house (the butler did it of course), but he says an invisisble alien from plant zod did it, and just made all the evidence look like it was the butler.

Does the alien qualify as a candidate explanation for the murder, as you cannot say it is impossible that the alien did it. Or do you need some demonstration that the alien exists, and is capable of fiddling with evidence?

The butler did it as in all good murders!

[Gordon]

NS,

Maybe I’m having a slow start this morning, but I can’t see the paradox. If we can’t say that anything is impossible (and I think we can’t no matter how undefined, apparently contradictory or incoherent to us) then it’s necessarily possible isn’t it?   

I think we just say that some things are not possibility-apt and leave at that until such times as there are grounds to take whatever it is moderately seriously - such as 'after life' notions.

[Nearly Sane]

NS,

Maybe I’m having a slow start this morning, but I can’t see the paradox. If we can’t say that anything is impossible (and I think we can’t no matter how undefined, apparently contradictory or incoherent to us) then it’s necessarily possible isn’t it?   

It's a bootstrap paradox

If you start with :
If you can't show something to be impossible, it is possible (note, I don't agree with that but for the purposes of illustrating the paradox, let's accept Prof D's starting position)
Followed by:
If something is possible, it rules out it being impossible
(Which you agreed with)
Then it follows that you have shown it by that logic to be impossible from a starting point of just not being able to show that it is impossible.

[Nearly Sane]

I have sufficient knowledge to say that it is possible.

Then demonstrate it to be possible

[jeremyp]

Jeremy,

Insofar as our grasp of logic makes it an absurdity that's true, but how would you know that that logic is universally applicable? How for example would you rule out "you" being a computer avatar that's just programmed to to think square circles are absurdities?   

The mathematical definition of a circle rules out it being a square and vice versa. These are names we apply to different phenomena. If you claim mathematics and logic are not universal, it still doesn't help your point because these are definitions we have arrived at using our logic and our mathematics. They would hold no meaning for some alien species with different logic and mathematical systems.

[jeremyp]

Then demonstrate it to be possible

I know I can't show it to be impossible. That knowledge leads me to concede it is possible.

[BeRational]

I know I can't show it to be impossible. That knowledge leads me to concede it is possible.

What if in reality, it is impossible? You have then conceded something that is just wrong.

Why do you feel to need to take a position on possible/impossible before a demonstration has been made.

Is it no better to just not know?

[Nearly Sane]

I know I can't show it to be impossible. That knowledge leads me to concede it is possible.

That's insufficient knowledge for a claim that it is possible. You do not know whether it is possible or not.

[jeremyp]

What if in reality, it is impossible? You have then conceded something that is just wrong.

That may be the case, but for the moment, I can't demonstrate it is impossible.

Why do you feel to need to take a position on possible/impossible before a demonstration has been made.

It's no skin off my nose to concede it may be possible. The important question is not "is it possible that there is an afterlife?" but "is there an afterlife?"

[jeremyp]

That's insufficient knowledge for a claim that it is possible.

No it isn't.

You do not know whether it is possible or not.

Based on the knowledge I have, I have to concede it is possible.

Let's take a more cut and dried statement:

"Is there an even number greater than two that cannot be written as the sum of two primes?"

For example

4 = 2 + 2
6 = 3 + 3
8 = 5 + 3
10 = 5 + 5
12 = 7 + 5

I cannot prove that such a number does not exist, nor can anybody else (yet), therefore I must concede that it is possible it does exist. This is in spite of the fact that such a number must be greater than 4 x 10¹⁸ - all even numbers smaller than that have been verified to be the sum of two primes.

[Nearly Sane]

No it isn't.Based on the knowledge I have, I have to concede it is possible.

Let's take a more cut and dried statement:

"Is there an even number greater than two that cannot be written as the sum of two primes?"

For example

4 = 2 + 2
6 = 3 + 3
8 = 5 + 3
10 = 5 + 5
12 = 7 + 5

I cannot prove that such a number does not exist, nor can anybody else (yet), therefore I must concede that it is possible it does exist. This is in spite of the fact that such a number must be greater than 4 x 10¹⁸ - all numbers smaller than that have been verified to be the sum of two primes.0

The example does not work, in fact it illustrates the opposite since it is based around your knowledge of numbers, and maths. What similar knowledge do you have as regards a claim about 'after life'?

[jeremyp]

The example does not work

Yes it does.

in fact it illustrates the opposite since it is based around your knowledge of numbers, and maths.

Nonsense. It's based around the fact that there is no proof of the impossibility.

What similar knowledge do you have as regards a claim about 'after life'?

I know quite a lot about various different versions of the afterlife and I know quite a lot about human physiology for a layman. Of course, my knowledge about these things is not as good as my knowledge about mathematics (I have a BSc in the latter), but that makes me more likely to concede an afterlife is possible.

[bluehillside Retd.]

NS,

Sorry it’s taken me a while to reply…

…It's a bootstrap paradox

If you start with :
If you can't show something to be impossible, it is possible (note, I don't agree with that but for the purposes of illustrating the paradox, let's accept Prof D's starting position)

I do start with that yes – though I’d probably qualify the “possible” with “conceptually” or “theoretically”. How for example would I eliminate the possibility that I’m merely programmed to think that square circles are impossible?

In other words, any statement of fact is necessarily delimited by our ability to know things to be facts and we’re not omniscient.     
 

Followed by:
If something is possible, it rules out it being impossible
(Which you agreed with)

Yes. I can’t rule out that anything is categorically impossible when there’s necessarily a theoretical possibility of being wrong about that – it’s the “unknown unknowns” problem. 

Then it follows that you have shown it by that logic to be impossible from a starting point of just not being able to show that it is impossible.

I’ve read this several times and still can’t make sense of it. Maybe it’s me, but can you clarify please? 

[ProfessorDavey]

That's insufficient knowledge for a claim that it is possible. You do not know whether it is possible or not.

But you can turn that around.

If there is insufficient knowledge to determine that a claim is impossible then it must be considered possible (the only other option being 'certain') until or unless it is determined to be either proven (certain) or falsified (impossible).

If you do not know that it is either impossible, or certain, then the only reasonable conclusion is that it is possible.

[BeRational]

But you can turn that around.

If there is insufficient knowledge to determine that a claim is impossible then it must be considered possible (the only other option being 'certain') until or unless it is determined to be either proven (certain) or falsified (impossible).

If you do not know that it is either impossible, or certain, then the only reasonable conclusion is that it is possible.

I disagree. I do not think that is reasonable.

I think the reasonable thing to do is withhold any conclusion.

Your reasonable beliefs or assumptions should be based on evidence and reason.

You are say that you have no evidence or reason to think that it is possible, but you are going to assume it is until shown that it is impossible.

This seems wrong to me.

[bluehillside Retd.]

Hi BR,

I disagree. I do not think that is reasonable.

I think the reasonable thing to do is withhold any conclusion.

Your reasonable beliefs or assumptions should be based on evidence and reason.

You are say that you have no evidence or reason to think that it is possible, but you are going to assume it is until shown that it is impossible.

This seems wrong to me

But why? The mistake here I think is to treat “impossible” and “possible” as opposites, when they’re not. “Impossible” is a claim of certainty – ie, that something definitively cannot be the case no matter the limitations on human understanding. “Possible” on the other hand is a probabilistic statement (albeit that the probability is unknown). That is, “impossible” and “possible” are in different epistemic categories.

In other words, if “impossible” cannot definitively be justified (and I think it can’t) then “possible” is the only other option.       

[BeRational]

Hi BR,

But why? The mistake here I think is to treat “impossible” and “possible” as opposites, when they’re not. “Impossible” is a claim of certainty – ie, that something definitively cannot be the case no matter the limitations on human understanding. “Possible” on the other hand is a probabilistic statement (albeit that the probability is unknown). That is, “impossible” and “possible” are in different epistemic categories.

In other words, if “impossible” cannot definitively be justified (and I think it can’t) then “possible” is the only other option.       

This can lead you to wrong conclusions I think

What if something actually is impossible, but you are not able to determine that. You then conclude that it is possible.

I think possible and impossible are opposites and both are claims that have the burden of proof.

If some thing cannot be shown to be either possible or impossible, then the conclusion is that is might be either, so no determination can be made.