  The situation appears to be very different in quantum mechanics, however. If the particles are taken to possess both their intrinsic and state-dependent properties in common, as suggested above, then there is a sense in which even the weakest form of the Principle, PII(1), fails (Cortes 1976; Teller 1983; French and Redhead 1988; for an alternative view, see van Fraassen 1985 and 1991). On this understanding, the Principle of Identity of Indiscernibles is actually false. Hence it cannot be used to effectively guarantee individuation via the state-dependent properties by analogy with the classical case. If one wishes to maintain that quantum particles are individuals, then their individuality will have to be taken as conferred by Lockean substance, primitive thisness or, in general, some form of non-qualitative haecceistic difference.