  Another ‘unorthodox’ approach incorporates the Bohmian interpretation of quantum mechanics and in particular it has been suggested that it might form the basis of an alternative conception of particle individuality in terms of their spatio-temporal trajectories. As is well known, attributing distinguishing spatio-temporal trajectories to quantum objects faces acute difficulties under the orthodox interpretation of quantum mechanics. On the Bohm interpretation, however, they are allowed; indeed, the only observable admitted is that of position. What this interpretation gives us is a dual ontology of point particles plus `pilot’ wave, where the role of the latter is to determine the instantaneous velocities of the former through the so-called ‘guidance equations’. These ‘complete’ the standard formulation of quantum mechanics so that, in addition to the quantum state, whose development is determined by the Schrödinger equation, there is also a set of single-particle trajectories, each of which is determined by the guidance equation, plus the initial positions of the particles (for a review see Cushing et al. 1996). Such an interpretation appears to provide a natural home for the metaphysical package which takes quantum objects to be individuals (see, for example, Brown et al. 1999) and, indeed, a form of PII(1) can now be defended against the above conclusion.