Awesome. I’m pretty sure you’re right; that’s the most convincing counterexample I’ve come across.
I have a weak doubt, but I think you can get rid of it:
let’s name the program FTL()
I’m just not sure this means that the theorem itself is assigned a probability. Yes, I have an oracle, but it doesn’t assign a probability to a program halting; it tells me whether it halts or not. What the Solomoff formalism requires is that “if (halts(FTL()) == true) then P(X|FTL()) = 1” and “if (halts(FTL()) == false) then P(X|FTL()) = 0″ and “P(FTL()) = 2^-K(FTL())”. Where in all this is the probability of Fermat’s last theorem? Having an oracle may imply knowing whether or not FTL is a theorem, but it does not imply that we must assign that theorem a probability of 1. (Or maybe, it does and I’m not seeing it.)
Edit: Come to think of it… I’m not sure there’s a relevant difference between knowing whether a program that outputs True iff theorem S is provable will end up halting, and assigning probability 1 to theorem S. It does seem that I must assign 1 to statements of the form “A or ~ A” or else it won’t work; whereas if the theorem S is is not in the domain of our probability function, nothing seems to go wrong.
In either case, this probably isn’t the standard reason for believing in, or thinking about logical omniscience because the concept of logical omniscience is probably older than Solomonoff induction. (I am of course only realizing that in hindsight; now that I’ve seen a powerful counter example to my argument.)
Awesome. I’m pretty sure you’re right; that’s the most convincing counterexample I’ve come across.
I have a weak doubt, but I think you can get rid of it:
let’s name the program FTL()
I’m just not sure this means that the theorem itself is assigned a probability. Yes, I have an oracle, but it doesn’t assign a probability to a program halting; it tells me whether it halts or not. What the Solomoff formalism requires is that “if (halts(FTL()) == true) then P(X|FTL()) = 1” and “if (halts(FTL()) == false) then P(X|FTL()) = 0″ and “P(FTL()) = 2^-K(FTL())”. Where in all this is the probability of Fermat’s last theorem? Having an oracle may imply knowing whether or not FTL is a theorem, but it does not imply that we must assign that theorem a probability of 1. (Or maybe, it does and I’m not seeing it.)
Edit: Come to think of it… I’m not sure there’s a relevant difference between knowing whether a program that outputs True iff theorem S is provable will end up halting, and assigning probability 1 to theorem S. It does seem that I must assign 1 to statements of the form “A or ~ A” or else it won’t work; whereas if the theorem S is is not in the domain of our probability function, nothing seems to go wrong.
In either case, this probably isn’t the standard reason for believing in, or thinking about logical omniscience because the concept of logical omniscience is probably older than Solomonoff induction. (I am of course only realizing that in hindsight; now that I’ve seen a powerful counter example to my argument.)