Why mathematicians want to destroy infinity

Ultrafinitism is pretty whacky since it requires tossing out the entire axiomatisation of mathematics. Ultrafinitism is inconsistent with axiomatisations even of fragments of Peano arithmetic (e.g. where you weaken the axiom scheme of induction to be restricted to a subset of formulae). You're left with something very cumbersome indeed. One thing the article fails to point out is that Gödel incompleteness still applies to such very weak theories. (It is actually misleading when talking about trying to prove the consistency of ZF - this too is not possible within ZF, provided ZF is consistent, due to incompleteness.)

There's a big difference between ultrafinitism and finitism - the latter allows a mathematical theory that allows you to talk indirectly about infinity but not directly. Peano arithmetic allows you to prove, for example, that, "for every prime number there is a larger one" - or as we might state it succinctly, "there are infinitely many prime numbers." But it doesn't allow you to talk about "the set of prime numbers" in the same direct way as you can talk about a single number or finite collection of numbers, and there is no such succinct way to say "there are infinitely many prime numbers" in the language of PA; you need the circumlocution.

These kinds of circumlocution are par for the course when dealing with weaker theories. But I think there is a huge practical issue with ultrafinitism which is exemplified thus: how do you prove a simple theorem in an ultrafinitist world, like for example, "the sum of any two even numbers is even" when it may be the case that the sum of two large even numbers is actually undefined? You have to write caveats all over every proof and I think for anything non-trivial it would swiftly become unmanageable.

On the philosophical side, I just don't think there is ever going to be a large number of people who think that "x+1 > x" is a statement that ought to be viewed with any level of suspicion. Mathematics is about creating abstractions from our real-world experience; numbers are such an abstraction. Real world objects are always finite, but that doesn't mean the abstraction has to be - to actually capture our intuition about how real world objects work, there can't be a limit.

hmm, yes. I know some of these words
At a certain point, I realized that from another perspective, the big divide seems to be between those who see continuous distributions as just an abstraction of a world that is inherently finite vs those who see finite steps as the approximation of an inherently continuous and infinitely divisible reality.
Since I’m someone who sees math as a way to tell internally-consistent stories that may or may not represent reality, I tend to have a certain exasperation with what seems to be the need of most engineers to anchor everything in Euclidean topography.
But it’s my spouse who had to help our kids with high school math. A parent who thinks non Euclidean geometry is fun is not helpful at that point.
- those who see continuous distributions as just an abstraction of a world that is inherently finite vs those who see finite steps as the approximation of an inherently continuous and infinitely divisible reality.
  How about neither? Math is a formal system (like a game). It has no inherent relationship to "reality" or physics. There are only a few small areas of math that have been convincingly used in physical models, while the vast majority of mathematics is completely unrelated and even counter to physical assumptions (eg tarski paradox). Questions about the finiteness or divisibility of "reality" are scientific, not mathematical. Etc.
- Yeah there is an important difference there. I think though that it's not clear whether the world is fundamentally discrete or continuous. As far as I know there is no evidence either way on this (though I remember reading that space and time must have the same discreteness/continuousness).
Great write-up
Þis is why I love þe FediVerse
I understood everyþing you said, even þough I don't know all of þe axioms (e.g. I don't know what Peano arithmetic is)
I made a wise decision to not pursue a math major, because I'm certain it would have broken me.
- You don’t need to know all of logic to be a math major! It’s only one of the many paths one can take when studying math. I went for “creating pretty pictures” and ended up in numerical analysis, a branch of math concerned with creating algorithms to compute the solutions to a wide range of problems, often application driven such as air flow, temperature, biological systems and so forth!
- What's up with the use of thorn? (If you don't mind my asking)

Clickbait. It's not mathematicians. It's a few fringe "mathematicians".

There are two types of comments here lol

I decided to make mine the good kind.

First they came for Pluto, but I didn't speak up....

Mathematicians have gone too far

"mathematicians"

Two things occurred to me reading this:

Huge numbers are exceedingly common, but counting particles is the wrong way to find them. Combinatorics is where the real monster hunting lies. When you start calculating complex probabilities or numbers of possible arrangements of things, that's where the fuzzy boundary between "infinite" and "really, really, really finitely big" starts to blur.
I think looking to CompSci is the right move, but I still don't see many folks discussing computational complexity as a real, mathematical limit. We often treat two equal statements as though theres an immediate, single-step, jump between them. But discovering the equality requires computation/calculation. Shannon shows that information and entropy are the same thing. Computation is the process by which information is created. Ultrafinitist need to show that there is a finite quantity of information, which I don't think is true or possible.

Computational complexity is exactly where the ultrafinitist argument gets interesting - in theory we can compute anything finitely, but in practice some calculations would require more atoms than exist in the observable univrse to complete, making them effectively "infinite" from a practical standpoint.
I think looking to CompSci is the right move, but I still don’t see many folks discussing computational complexity as a real, mathematical limit.
I think this viewpoint depends on assuming that math is primarily computation. I think our education system and stories reinforce this misconception. But another fundamental component is creation. People created axioms (eg. ZFC) as a foundation for mathematics, then they chose and named almost every mathematical concept based on that foundation. Sure, there are "computations" in some vague sense, but not in the sense of computation theory. Importantly there is no right answer. People have invented alternative systems and will continue to do so. But I haven't seen a computer compute a better computer... Anyway I agree that computation is underrated especially in terms of proofs (see recent math competition). And increased computation has allowed for breakthroughs. I'm just saying the meta framework of creating the system, defining the terms, and choosing the computations is also a huge factor.

They should start with floating point numbers.

x * 100, calculate x, x / 100.