 We have already seen how the dynamical approach, qua programme of ontological reduction, is supposed to play out in the context of theories with fixed spacetime structure, including both Newtonian theories and STR. We have also witnessed Brown and Pooley’s concerns about the ability of a substantival spacetime to explain facts about the behavior of matter. These concerns are motivated by apparent problem cases, in which the symmetries of a substantival spacetime seem to come apart from those of the dynamical laws governing matter. Such cases include: (i) Newtonian mechanics set in Newtonian spacetime (Read 2020a); (ii) the Jacobson-Mattingly theory (Jacobson &amp; Mattingly 2001), in which dynamical symmetries are a subset of spacetime symmetries, as a result of the presence of an additional (dynamical) symmetry-breaking vector field (Read, Brown &amp; Lehmkuhl 2018).