Comment by k_bx
4 days ago
> All of modern mathematics is built on the foundation of set theory, the study of how to organize abstract collections of objects
What the hell. What about Type Theory?
4 days ago
> All of modern mathematics is built on the foundation of set theory, the study of how to organize abstract collections of objects
What the hell. What about Type Theory?
Type theory is actually a stronger axiomatic system than ZFC, and is equiconsistent with ZFC+ a stronger condition.
See this mathoverflow response here https://mathoverflow.net/a/437200/477593
To echo the sibling comment, that answer is specifically referring to the type theory behind Lean (which I’ve heard is pretty weird in a lot of ways, albeit usually in service of usability). Many type theories are weaker than ZFC, or even ZF, at least if I correctly skimmed https://proofassistants.stackexchange.com/a/1210/7.
"the study of how to organize abstract collections of objects" is not really a great explanation of set theory. But it is true that the usual way (surely not the only way) to formalize mathematics is starting with set-theoretic axioms and then defining everything in terms of sets.
"Usual", "most common by far" etc. are all great phrases, but not "all of mathematics", esp when we talk about math related to computer science
Math related to CS is typically formalized starting with set theory, just like other branches of math.
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Is there a collection of type theory axioms anywhere near as influential as ZF or ZFC?
Sure, but is discarding Type Theory and Category Theory really fair with a phrase like "All of modern mathematics"? Especially in terms of a connection with computer science.
Arguably, type theory is more influential, as it seems to me all the attempts to actually formalize the hand-wavy woo mathematicians tend to engage in are in lean, coq, or the like. We've pretty much given up on set theory except to prove things to ourselves. However, these methods are notoriously unreliable.
Regardless of the name, descriptive set theory does not seem to have all that much to do with "set theory" in a foundational sense; it can be recast in terms of types and spaces with comparative ease, and this can be quite advantageous. The article is a bit confusing in many ways; among other things, it seems quite obviously wrong to suggest that recasting a concept that seems to be conventionally related to mathematical "infinities" in more tangible computational terms is something deeply original to this particular work; if anything, it happens literally all the time when trying to understand existing math in type-theoretic or constructive terms.
the empirical modern mathematics are build on set theory, type and category theory are just other possible foundations
Most modern mathematicians are not set theorists. There are certain specialists in metamathematics and the foundations of mathematics who hold that set theory is the proper foundation -- thus that most mathematical structures are rooted in set theory, and can be expressed as extensions of set theory -- but this is by no means a unanimous view! It's quite new, and quite heavily contested.
My impression (as a dilettante programmer without relevant credentials) is that there isn't really any question about whether mathematical structures can be rooted in set theory, or can be expressed as extensions of set theory. Disputes about foundations of mathematics are more about how easy or elegant it is to do so. (And in fact my impression is they're mostly about subjective, aesthetic considerations of elegance rather than practical considerations of how hard it is to do something in practice, even though the discussion tends to be nominally about the practical side. Quite similar to disputes about programming languages in that respect.)
yes of course, I just mean that from the set of foundational mathematics, set theory is the strongest one empirically, but that there are other options (possibly better)