Description: Law of identity (reflexivity of class equality). Theorem 6.4 of Quine
p. 41.

This is part of Frege's eighth axiom per Proposition 54 of Frege1879
p. 50; see also biid . An early mention of this law can be found in
Aristotle,Metaphysics, Z.17, 1041a10-20. (Thanks to Stefan Allan and
BJ for this information.) (Contributed by NM, 21-Jun-1993)(Revised by BJ, 14-Oct-2017)