Abstract

Two different concepts of distinguishability are often mixed up in attempts to derive in quantum mechanics the symmetry of the wave function from indistinguishability of identical particles. Some of these attempts are analyzed and shown to be defective. It is argued that, although identical particles should be considered as observationally indistinguishable in symmetric states, they may be considered to be conceptually distinguishable. These two notions of distinguishability have quite different physical origins, the former one being related to observations while the latter has to do with the preparation of the system.