Theoretical Basis of the Symmetrization Postulate

The postulate of symmetrization for identical particles in quantum mechanics does not necessarily follow from the condition of indistinguishability. Greenberg and Messiah have shown that, under suitable conditions, the selection rule implied by the postulate of symmetrization actually follows from the indistinguishability complemented by some broad assumptions about the quantum system. The aim of this paper is to show that the most restrictive of these extra assumptions, namely, $\mathrm{PCT}$ or time-reversal invariance, is unnecessary.