Talk:Class Equality is Symmetric

From ProofWiki
Jump to navigation Jump to search

Isn't this just an instance of equality being symmetric? --prime mover 06:04, 7 August 2012 (UTC)

Yes, but it is purely set theoretical. It does not depend on Leibniz's Law. For rigor's sake, we shouldn't confuse class equality and $=$ from Leibniz's Law until we can prove a special case of Leibniz's Law as a theorem in set theory (we can now, using Substitutivity of Class Equality). That was the basis for the approach here. --Andrew Salmon 06:11, 7 August 2012 (UTC)
Then this page needs to state explicitly how it is defining $=$. --GFauxPas 06:45, 7 August 2012 (UTC)
Done. --Andrew Salmon 06:48, 7 August 2012 (UTC)