Yeah. It's pretty foundational. e.g. https://en.wikipedia.org/wiki/Aleph_number https://en.wikipedia.org/wiki/Aleph_number I guess it's possible to teach it wit

Yeah. It's pretty foundational. e.g. https://en.wikipedia.org/wiki/Aleph_number https://en.wikipedia.org/wiki/Aleph_number I guess it's possible to teach it without going through the proof.