Talk:Cantor-Bernstein-Schröder Theorem/Lemma

Is there a theorem somewhere proving the form of LEM I used in the second lemma? That is:

$\vdash (x \land y) \lor (x \land \lnot y) \lor (\lnot x \land y) \lor (\lnot x \land \lnot y)$

The middle of this proof doesn't seem quite the place for it. --Dfeuer (talk) 20:37, 11 March 2013 (UTC)

No, it doesn't - perhaps best to write a page for it. Such a page would belong in Propositional Logic. --prime mover (talk) 20:41, 11 March 2013 (UTC)

You name it, I'll write it. --Dfeuer (talk) 20:56, 11 March 2013 (UTC)