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Logical Limbo (Posted on 2002-08-12) Difficulty: 4 of 5
Prove that either

a) this problem is solvable

or

b) this problem is unsolvable

See The Solution Submitted by Cheradenine    
Rating: 3.2000 (15 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: Well..... | Comment 10 of 33 |
(In reply to Well..... by Dulanjana)

> The only possible situations are given by "a" and "b" (No other situation can occur). So if one is false the other is True. A truth is provable. Therefore this problem is solvable.

Not so. Goedel managed to really irritate the mathematics community by essentially proving that there are well-formed propositions in number theory and formal logic which can neither be proven true nor false. Essentially, he found a way to translate "This is a false statement" into the language of mathematics. There are other examples of such weirdness. For example, it's impossible to write a computer program that will determine reliably whether another computer program will enter an infinite loop. I'd also be impressed by any computer program that can solve the MU puzzle I had previously submitted, without special help.

Self-referential problems often lead to a hairy mess. Clearly, the way to attack this problem is not by assuming (b), as it leads to a contradiction. What's not so clear is whether we can go through (a), which does not lead to any contradictions, but does not necessarily provide enough positive statements to generate a proof.
  Posted by friedlinguini on 2002-08-13 03:15:46

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