Volenta wrote:Isn't Matt also making an error in his logic? His position is that he can not prove he's not a brain in a vat, but when Sye asks whether he could be, Matt says it can't.
I think Sye asked if Matt thought he was a brain in a vat, and Matt said no, he doesn't believe that is true.
Volenta wrote:Matt says that if something isn't proven to be false, that this doesn't mean it is possible.
That's true.
If something is proven to be false, it is impossible.
If something is proven to be true, of course it is possible.
If there is no truth either way, then we don't know if something is or is not possible.
For example, warp drives of some kind may or may not be possible. We don't know.
In common English, people say "it's possible" when they really mean "it's possible as far as I know", or "I don't know that it is impossible".
Whether we know something or not, is is true that it is either possible or impossible; there isn't any middle ground there. But as far as knowledge claims go, there is a 'middle ground' of neutrality in asserting neither- that the possibility or impossibility of a matter is unknown.
This is a case of Sye trying to shift the burden of proof, and make out as if Matt is making a knowledge claim on the subject.
It seems that Matt did a poor job of explaining this.
Volenta wrote:if you claim to know something isn't possible, you must be able to prove it to be false.
Correct. If you assert that something is impossible, you should be able to prove it to be false.
However, Matt didn't say that. He said the lack of proof that something is false doesn't make it possible (e.g. capable of being true- which it may or may not be in fact)
There are many examples of this in mathematics and science.
Warp drive is a good example.
Just because we can't prove that it's impossible, doesn't automatically mean it's possible.
Worm holes are the same.
A common example of it used to make illogical claims:
Nobody has proven that it is impossible -> therefore it's possible -> therefore it can be done!
This is a logical fallacy. It's a form of
ambiguity with regards to the usage of the word "possible". As well as
shifting the burden of proof.
P = NP vs. P ≠ NP is similar, in the domain of mathematics.
Although, typically only computer scientists and mathematicians understand that, and they're less likely to make the mistake in assuming something without proof.
Volenta wrote:Certainly your default position should be that something isn't true until proven otherwise (and not vice versa) because of the burden of proof,
Correct. And he does.
Volenta wrote:but you can't rule out the possibility.
This statement is begging the question; it assumes that it is possible, without it having been proven to be possible.
You can't rule out a possibility if it hasn't been shown to be possible in the first place.
If it hasn't been shown to be impossible either, all you can do is say you don't know if it is or isn't possible.
I can make a very compelling argument against hard solipsism (I'm not sure if Matt can, but I wouldn't be surprised if he hasn't heard one before).
Hard solipsism may be logically impossible- as he stated, he doesn't know either way.