 But this “official view” seems at odds with a second “unofficial” way Polger and Shapiro cash “relevant differences”: “a matter of whether a property has an explanatory role with respect to a function” (Couch 2018: 424). This “unofficial” understanding, Couch insists, sees relevance as an explanatory relation between properties or kinds in nature, and thus not merely a matter of what scientists “tell us”. These two readings of “relevant differences” strike Couch as making it unclear how the Official Recipe will apply to Polger’s and Shapiro’s own examples of multiple realized kinds.