Dark Matter = Modified Gravity? Scrutinising the spacetime-matter
  distinction through the modified gravity/ dark matter lens
  This paper scrutinises the tenability of a strict conceptual distinction
between space(time) and matter via the lens of the debate between modified
gravity and dark matter. In particular, we consider Berezhiani and Khoury's
novel 'superfluid dark matter theory' (SFDM) as a case study. Two families of
criteria for being matter and being spacetime, respectively, are extracted from
the literature. Evaluation of the new scalar field postulated by SFDM according
to these criteria reveals that it is as much (dark) matter as anything could
possibly be, but also$-$below the critical temperature for superfluidity$-$as
much (of a modification of) spacetime as anything could possibly be. A sequel
paper examines possible interpretations of SFDM in light of this result, as
well as the consequences for our understanding of (the importance of) the
modified gravity/ dark matter distinction and the broader spacetime-matter
distinction.
