 The justification usually given for this is that the only way to keep track of the individual particles and thereby retain their individuality is by following their trajectories, which of course one cannot and must not do, and in any case does not have, in standard quantum mechanics. (Like so many arguments used to justify various claims in quantum mechanics, this sort of argument, with its positivistic slant, is rather weak. Its conclusion, however, is quite solid.) On this basis one often hears it maintained that Bohmian mechanics, because its particles have trajectories (deterministic ones to boot), is unable to deal with identical particles.