News for hackers. Stuff that matters.
Re:What is the Axiom of Choice? by pron on Friday July 16, 2021 @09:59AM (#27856273)
> ... then that person rejects the Axiom of Choice.

You're looking at it from a philosophical perspective where people care about whether the axiom is "true" or not. Other approaches to mathematics don't care, because they view its value not in some metaphysical notion of truth but in utility. They might say: this proof requires the axiom of choice and that proof doesn't, without assigning either one any value beyond utility (where utility might be, in some case, just their intellectual edification). I think this is what the article is trying to drive at as well. We can't "accept" or "reject" the axiom of choice based on some philosophical grounds, because those philosophical grounds would need to involve infinities [1], which, themselves, are not philosophical but mathematical. We either choose to use it or not based not on where we come from but on where we want to go.

[1]: The view that mathematical philosophy could be derived from core basic principles outside of mathematics was called Logicism, and was favoured by Bertrand Russell. Unfortunately, mathematical systems without some mathematical (i.e. non-"logical") axioms are quite limited, and almost all of them include at least one mathematical axiom, usually one that is equivalent to the existence of the natural numbers.

Re:What is the Axiom of Choice? by cannabis_sam on Friday July 16, 2021 @10:21AM (#27856487)
>they view its value not in some metaphysical notion of truth but in utility.

Isn’t this a philosophical perspective?

Re:What is the Axiom of Choice? by pron on Friday July 16, 2021 @10:41AM (#27856704)
It is a perspective in the philosophy of mathematics that rejects the idea that all of mathematics is necessarily anchored in philosophical truths beyond itself.
Re:What is the Axiom of Choice? by cannabis_sam on Friday July 16, 2021 @11:32AM (#27857316)
> It is a perspective in the philosophy of mathematics

So it is a philosophical perspective…?

Re:What is the Axiom of Choice? by pron on Friday July 16, 2021 @12:31PM (#27858001)
Of course. I think you may have misread my original comment, which compared two philosophical perspectives on mathematics, one philosophical perspective that views mathematics as an expression of some truth beyond mathematics, and another philosophical perspective that sees mathematics as a tool to achieve some ends.
Re:What is the Axiom of Choice? by cannabis_sam on Friday July 16, 2021 @12:46PM (#27858179)
> not in some metaphysical notion of truth but in utility.

So one is not metaphysical because it is a tool to achieve ends?

(Sorry, if I come across as argumentative, I don’t mean to. I’m genuinely just curious.)

Re:What is the Axiom of Choice? by jfengel on Friday July 16, 2021 @01:36PM (#27858846)
It is a metaphysical statement about whether metaphysics is important in this instant, rather than being dispensed with in favor of something useful. It's picking a particular metaphysics rather than being bogged down in the meta-metaphysical question of the necessity of metaphysics.

Or at least, that's the way I read it. The question of the value of metaphysics is an open one, which easily comes to dominate other questions if allowed to. I think the OP is saying, "I'm going to make a metaphysical commitment, and let other people worry about whether doing so is good metaphysics." (And there's good reason to think that it isn't -- but it's unclear whether that matters, or should matter.)

Re:What is the Axiom of Choice? by cannabis_sam on Sunday July 18, 2021 @08:45AM (#27872467)
Yeah, I misread. Thanks for helping me understand!
Re:What is the Axiom of Choice? by pron on Friday July 16, 2021 @02:34PM (#27859581)
For some reason you keep skipping the qualifiers in what I write. It does not say "some metaphysical notion" but "some metaphysical notion of truth". In other words, what matters isn't whether an axiom is "true" or not in some way that is external to mathematics, but what use could be made of that axiom. You did the same above; I didn't write "from a philosophical perspective" but "from a philosophical perspective where ..."
Re:What is the Axiom of Choice? by cannabis_sam on Saturday July 17, 2021 @07:33AM (#27865082)
> For some reason you keep skipping the qualifiers in what I write.

My apologies, but I think I’ve understood where I misread your comment. Thanks for being patient!

Re:What is the Axiom of Choice? by eeegnu on Friday July 16, 2021 @04:31PM (#27860875)
> Unfortunately, mathematical systems without some mathematical (i.e. non-"logical") axioms are quite limited

What's an example without any axioms? It doesn't seem like you can do anything without say ∀x: x=x (which I believe is reciprocal identity.)

Re:What is the Axiom of Choice? by pron on Saturday July 17, 2021 @05:43AM (#27864662)
I think Russell would consider that a logical axiom, and it commonly is an axiom of predicate logic with equality. BTW, by "logic", he didn't mean just a specific set of familiar axioms, but any axiom which could be considered "obviously true" and didn't involve numbers specifically. https://en.wikipedia.org/wiki/Logicism