 Mark Couch (2018) worries about Polger and Shapiro’s general characterization of multiple realization in terms of the taxonomies offered by different sciences, as opposed to more typical accounts in terms of properties or kinds in the world. About this shift, Couch first points out that scientists in any given field aren’t always in agreement about how to taxonomize the phenomena they address. So appealing to “scientists’ taxonomies” might not be sufficient, and philosophers might be forced back to considering “independently existing kinds” (2018: 421). Polger and Shapiro’s refocused account also might not address what has interested philosophers about multiple realization, namely, concerns about metaphysical relations holding between independently existing properties and kinds; independent, that is, of any taxonomic practices. This leads Couch to worry about Polger and Shapiro’s account of “relevant differences” in their “Official Recipe”, especially their account of how we decide when this condition has been met. He senses an internal tension lurking here. On the one hand, 