ArisKatsaris comments on Edward Nelson claims proof of inconsistency in Peano Arithmetic - Less Wrong

13 Post author: JoshuaZ 27 September 2011 12:46PM

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Comment author: ArisKatsaris 28 September 2011 12:34:22PM 1 point [-]

If Nelson is right, then people should stop using 3^^^3 in their thought experiments.

...I don't understand how this can be. 3^^3 is just (3^(3^3))= 3^27 = 7625597484987 And 3^^^3 is just (3^(3^(3^(... 7625597484987 times ...))))

Superexponentiation is just made of exponentiation many times. And exponentiation is made of multiplication, and multiplication is made of addition.

How can superexponentiation be made invalid without making invalid even normal addition?

Comment author: [deleted] 28 September 2011 12:43:25PM 3 points [-]

I can say more if you want, but maybe see here and here for an explanation.

Comment author: JoshuaZ 28 September 2011 01:42:21PM *  1 point [-]

Any finite calculation of superexponentiation will be valid. But as I understand it you can't in general in Nelson's formulation prove that superexponentation is well-defined in general.