benelliott 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: benelliott 27 September 2011 02:53:40PM 2 points [-]

To date there are 733 axioms

How do you get to 733 axioms? Maybe I'm being stupid, but doesn't PA run on just 5?

Comment author: Sniffnoy 28 September 2011 02:42:40AM 4 points [-]

Strictly speaking, PA uses infinitely many axioms -- the induction axiom is actually an axiom schema, one axiom for each predicate you can plug into it. If you actually had it as one axiom quantifying over predicates, that would be second-order.

Comment author: [deleted] 28 September 2011 03:03:07AM 1 point [-]

I think that Nelson denies that there is a completed infinity of predicates that you can plug into the schema.

Comment author: Sniffnoy 28 September 2011 03:57:44AM 5 points [-]

Well, you'd certainly only need finitely many to prove inconsistency.

Comment author: [deleted] 27 September 2011 03:00:50PM 3 points [-]

I think 733 is counting axioms, definitions, and theorems all.

Comment author: benelliott 27 September 2011 03:07:30PM 1 point [-]

That would explain it.

Comment author: ArisKatsaris 27 September 2011 02:59:29PM 2 points [-]

It said "733 axioms, definitions, and theorems"

I'm guessing 733 is the sum of the axioms, definitions and theorems, not just the axioms alone.