A monothetic definition of religion with multiple criteria, which treats religion as a multidimensional complex, can be double-sided when it includes both substantive and functional approaches. In this definition, a set of beliefs about reality influences the behavior of practitioners. The definition of William James (religion involves a belief in an unseen order per James) and Clifford Geertz (Five elements of a religion per Clifford Geertz) are both double-sided.
Schilbrack, K. (2022). The Concept of Religion. In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Summer 2022). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/sum2022/entries/concept-religion/
It is worth noting that when a monothetic definition includes multiple criteria, one does not have to choose between the substantive and functional strategies for defining religion, but can instead include both. If a monothetic definition include both strategies, then, to count as a religion, a form of life would have to refer to a distinctive substantive reality and also play a certain role in the participants’ lives. This double-sided approach avoids the result of purely substantive definitions that might count as religion a feckless set of beliefs (for instance, “something must have created the world”) unconnected from the believers’ desires and behavior, while also avoiding the result of purely functional definitions that might count as religion some universal aspect of human existence (for instance, creating collective effervescence or ranking of one’s values).
William James’s definition of religion (“the belief that there is an unseen order, and our supreme good lies in harmoniously adjusting ourselves thereto”) is double-sided in this way, combining a belief in the existence of a distinctive referent with the spiritual disciplines with which one seeks to embody that belief. Geertz’s definition of religion also required both substantive and functional aspects, which he labelled “worldview” and “ethos” (1973: ch. 5). To treat religion as “both/and” in this way is to refuse to abstract one aspect of a complex social reality but instead recognizes, as Geertz puts it, both “the dispositional and conceptual aspects of religious life” (1973: 113).
These “monothetic-set definitions” treat the concept of religion as referring to a multifaceted or multidimensional complex.