 With respect to the unity argument, Koslicki (2015) and J. Wilson (2016a) challenge the second premise, arguing that, even if the metaphysical relations (or some sub-collection thereof) are substantially unified, this on its own wouldn’t give us a good reason to posit a generic relation of grounding as a unifier. J. Wilson (2014) challenges the first premise as well, arguing that there is a class of metaphysical relations, what she calls the small-g grounding relations, that are neither terminologically, formally, nor metaphysically unified. Relatedly, Turner (2016) describes various differences in the way certain kinds of grounding claims behave, ultimately distinguishing between two forms of grounding, dependence-grounding and realization-grounding. (For non-skeptical rejoinders to these challenges, see Raven 2017, and Schaffer 2016b.)