I have to quibble here - math uses the = sign for equality, which is not the same concept is equivalence.

Roughly, things that are equal are "the same" whereas things that are equivalent are "interchangeable".

The "This is my rifle. There are many like it, but this one is mine," creed from a famous evil institution starts with a rumination on these ideas.

If you care about these matters, I cannot recommend Dennett's most recent book enough!

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

It sums up his life's work, it's entertaining while extremely chewy, and if he reiterates his work from "Freedom Evolves", he will also prove the independence of "free will" and "determinism" again - that a deterministic universe is consistent with free will.

I'm not even a chapter into it, mainly because I read a page and then think about it. And yet I feel I could read it like a novel if I wanted, it's so clear.