  In resisting attempts to explain the unity of a whole in terms of a
multiplicity of interacting parts, quantum mechanics calls for an explanatory
concept that proceeds in the opposite direction: from unity to multiplicity. It
concerns the process by which what Sellars called the Manifest Image of the
world comes into being. This process consists in the progressive
differentiation of an intrinsically undifferentiated entity. By entering into
reflexive spatial relations, this gives rise to (i) what looks like a
multiplicity of relata if the reflexive quality of the relations is not taken
into account, and (ii) what looks like a substantial expanse if the spatial
quality of the relations is reified. If there is a distinctly quantum domain,
it is a non-spatial and non-temporal dimension across which the transition from
the unity of this entity to the multiplicity of the world takes place. Instead
of being constituents of the physical world, subatomic particles, atoms, and
molecules are instrumental in its manifestation. These conclusions are based on
the following interpretive principle: whenever calculating probabilities calls
for the addition of amplitudes, the distinctions we make between the
alternatives lack objective reality. Applied to alternatives involving
distinctions between regions of space, this principle implies that the
spatiotemporal differentiation of the physical world is incomplete: the
existence of a real-valued spatiotemporal background is an unrealistic
idealization. This guarantees the existence of observables whose values are
real *per se*, as against "real by virtue of being indicated by the values of
observables that are real *per se*." Applied to alternatives involving
distinctions between things, it implies that, intrinsically, all fundamental
particles are numerically identical and thus identifiable with the
aforementioned undifferentiated entity.
