This paper pushes back against the Democritean-Newtonian tradition of
assuming a strict conceptual dichotomy between spacetime and matter. Our
approach proceeds via the more narrow distinction between modified
gravity/spacetime (MG) and dark matter (DM). A prequel paper argued that the
novel field Ī¦ postulated by Berezhiani and Khoury's 'superfluid dark
matter theory' is as much (dark) matter as anything could possibly be, but
alsoābelow the critical temperature for superfluidityāas much (of a
modification of) spacetime as anything could possibly be. Here we introduce and
critically evaluate three groups of interpretations that one should consider
for such Janus-faced theories. The consubstantiality interpretation holds that
Ī¦ is both (dark) matter and a modification of spacetime, analogously to
the sense in which Jesus (according to catholicism) is both human and god. The
fundamendalist interpretations consider for each of these roles whether they
are instantiated fundamentally or emergently. The breakdown interpretations
focus on the question of whether Ī¦ signals the breakdown, in some sense to
be specified, of the MG-DM dichotomy and perhaps even the broader
spacetime-matter distinction. More generally, it is argued that hybrid theories
urge a move towards a single space of theories, rather than two separate spaces
of spacetime theories and matter theories, respectively.Comment: 46 page