  Saunders (2003a, 2003b and 2006) argues that there is a weakened form of PII (discussed by Quine 1976) that is satisfied even by electrons in the singlet state described above. The notion of ‘weak discernibility’ applies to objects that satisfy some irreflexive relation (a relation such that xRx does not obtain for every x). The relation of having opposite spin that is had by electrons in the singlet state is clearly such an irreflexive relation and Saunders argues that, since by Leibniz's law, the holding of an irreflexive relation aRb entails the existence of distinct relata a and b, then the electrons are individuals, even though in so far as they are individuals it is the relations among them that account for this.