Re: ...impressed silence...
Originally posted by sparkle
*headspin* Wow, after translating your text to my own language and reading it over and over in both it and English I am still confused and not sure I got you. I have two suggestions:
1.Could you start over (should I dive for cover here?) with the „inner“ hypothesis („it is impossible to prove anything“) and then, once you complete that move to the outer one (the possibility of proving the „inner statement“)? It would IMHO look like that:
it is impossible to prove anything - three options: true, false, neither.
Then IF true, the possibility to prove...
IF not true, the possibility to prove,
for neither, hm, I don’t know. Should be a conclusion in a sense. I noted you did that in a way, but it seems not structured enough to me. I had problems following you through the „inner“ and „outer“ statements.
2. Could you be a bit more specific? For me the way of thought was: It cannot be impossible to prove the impossibility of anything, because if there is a single incident where it would be possible, it is impossible to be impossible to prove the impossibility of anything *sigh* and therefore it would be possible to prove the impossiblity of something. *headsteam* Anyway, before it gets complicated again, I declare I will sacrifice one of my examples for you to rip to pieces. Deal?
OK, here goes.
The problem is concerned with the relationship between truth and proof. It is an attempt to reproduce Goedel's proof that they are not the same thing without all the mathematics.
To put it imprecisely Goedel proved that in any system of thinking capable of being translated into a formal axiomatic system of proofs, (ie all 'rational' ways of proving things about the world) there are things that are true which cannot be proved to be true, and that all systems of proof (and thus all proofs) are flawed. (Some might argue with this way of putting it but I'll be here all day if I try to justify this interpretation - I'll come back to it if you disagree).
Please note that this discussion applies to axiomatic systems only, systems that refer outside of themselves ('synthetic' systems in Kant's sense, rather than analytic systems, statements in which are simply tautological and thus completely decidable by proof).
In any system of proof it is possible to express the statement 'it is impossible to prove anything'. However in all systems of proof it is impossible to prove this statement to be true. This is for logical reasons.
One can always assert that 'it is impossible to prove that it is impossible to prove anything' and know that it is true. If it were false it would be self-contradictory, since if it were false then one could assert the opposite to be true, namely that 'it is possible to prove that it is impossible to prove anything'. This assertion is plainly nonsensical since if it is true it is false.
From this we might conclude that the assertion 'it is impossible to prove that it is impossible to prove anything' must be true. We might also therefore conclude that it IS possible to prove some things. (By 'prove' I mean completely and rationally prove).
But this is jumping the gun. There are two reasons that our assertion might be true. Let's call the assertion, which can be made within any rational system of thinking based on proof of truth and falsity you choose, A(S).
A(S) seems definitely true for the logical reasons given. Logically it cannot be false. Thus whether we can completely prove anything is an empirical matter. It is in principle impossible to prove otherwise, since to prove otherwise is to contradict ourselves.
But A(S) may also be true because it is actually TRUE. In other words, and despite the fact that we can never prove it, it may really be the case (as Goedel suggests) that we cannot prove anything completely by any rational method of proof. In other words A(S) may be just one example of what we cannot prove.
Thus although the assertion cannot be false (and therefore Goedel cannot have proved that proof is impossible) we still know nothing about whether it is possible to prove anything or not, since A(S) would remain true whether or not it is impossible to prove anything.
That is to say that although we cannot PROVE that proof is impossible it may yet be true that a complete proof of anything about the universe is impossible.
From Goedel we know that we can know things which we cannot prove. The question therefore arises of whether it is possible to KNOW that all proofs based on rational systems of truth and falsity must ultimately fail, without being able to prove it.
To update my example-
Let us say that
p = any complete proof of the impossibility of proving anything
and
s = any system of logic within which p may be constructed
If p is true then it is a complete proof, if it is false then it is not.
If s is true then it is logically consistent and can in theory produce a true p , if false it is inconsistent and cannot produce a true p.
Then
If p is provably true then s is provably false, (it must be inconsistent since p is logically self-contradictory). However if s is provably false then p is not provably true (since the system of proof is logically flawed). Thus p cannot ever be proved to be true.
BUT - there is another interpretation.
If p is true but not provably so then all s's are false. (This is the link with Eastern philosophies, most of which assert that all proof is based on dualism (truth and falsity) and thus that all knowledge derived from such proofs is suspect and subordinate to what we know from our own unprovable experience).
This leaves us in the position that IF it is the case that all complete proofs are impossible then we will never be able to prove it.
This means that when someone claims that 'it is impossible to completely prove anything' (and thus that all third-person proof-based systems of rational thinking are ultimately NOT capable of completely proving anything logically) it is impossible to refute them, since we cannot expect them to be able to prove it. The fact that they cannot prove it is part of their evidence.
(This is getting away from me but I'll keep going).
If a priori we know that we cannot refute their claim (since they can offer no proof of it which we can then disprove) then all proofs are ultimately suspect.
If all proofs are suspect in this way then it is true that it is impossible to prove anything, even though we cannot prove it.
Thus we have solved our problem in the same way as Goedel. he showed that it is possible to KNOW that a Goedel sentence is true although it is impossible prove it to be true (within the existing system of proof). In the same way it seems to be (theoretically) possible to KNOW that all rational proofs of anything (non-trivial) are impossible but be unable to prove it.
Phew! This went wrong again but I'll leave it as it is. I cannot clinch the argument because I'm arguing that all arguments are unclinchable. Anyway please argue with it because it might help sort out the confusion. There must be a simpler way of putting it but I can't find it.