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Comment by dumstick | Hacker News Reader

Is this a joke or are you deeply interested in some ZFC variant that im unaware of? We absolutely need infinity to make a ton of everyday tools work, its like saying we dont need negative numbers because those dont exist either.

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A ZFC variant without infinity is basically just PA. (Because you can encode finite sets as natural numbers.) Which in practice is plenty enough to do a whole lot of interesting mathematics. OTOH by the same token, the axiom of infinity is genuinely of interest even in pure finitary terms, because it may provide much simpler proofs of at least some statements that can then be asserted to also be valid in a finitary context due to known conservation results.

In a way, the axiom of infinity seems to behave much like other axioms that assert the existence of even larger mathematical "universes": it's worth being aware of what parts of a mathematical development are inherently dependent on it as an assumption, which is ultimately a question of so-called reverse mathematics.

There are a couple philosophies in that vein, like finitism or constructivism. Not exactly mainstream but they’ve proven more than you’d expect

https://en.wikipedia.org/wiki/Finitism

https://en.wikipedia.org/wiki/Constructivism_(philosophy_of_...

That looks closer to https://en.wikipedia.org/wiki/Ultrafinitism

There’s tons of variants of ZFC without the “infinity”. Constructivism has a long and deep history in mathematics and it’s probably going to become dominant in the future.

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