 The converse of Leibniz’s Law, the principle of the identity of indiscernibles, that if everything true of x is true of y, x is identical with y, is correspondingly trivial if “what is true of x” is understood to include “being identical with x” (as required if Leibniz’s Law is to characterise identity uniquely among equivalence relations). But often it is read with “what is true of x” restricted, e.g., to qualitative, non-relational, properties of x. It then becomes philosophically controversial. Thus it is debated whether a symmetrical universe is possible, e.g., a universe containing two qualitatively indistinguishable spheres and nothing else (Black 1952).