 In Bohmian mechanics the wave function, obeying Schrödinger’s equation, does not provide a complete description or representation of a quantum system. Rather, it governs the motion of the fundamental variables, the positions of the particles: In the Bohmian mechanical version of nonrelativistic quantum theory, quantum mechanics is fundamentally about the behavior of particles; the particles are described by their positions, and Bohmian mechanics prescribes how these change with time. In this sense, for Bohmian mechanics the particles are primary, or primitive, while the wave function is secondary, or derivative. (Bohmian mechanics, like classical mechanics, is thus a theory grounded in a primitive ontology, for Bohmian mechanics one of particles described by their positions. This terminology was introduced in Dürr et al. 1992a. For more on the notion of primitive ontology, see Allori et al. 2008 and Allori 2015.)