In Genealogies of religion: Discipline and Reasons of Power in Christianity and Islam, Talal Asad states that his aim is “to problematize the idea of an anthropological definition of religion by assigning that endeavor to a particular history of knowledge and power (…) out of which the modern world has been constructed” (Asad, 54). For Asad, each historical period is characterized by a specific interplay between religious power and knowledge, and it is through an appreciation of this interplay within a particular historical period that we may arrive at a definition of religion applicable to that period: “What we call religious power was differently distributed and had a different thrust. There were different ways in which it created and worked through legal institutions, different selves that it shaped and responded to, and different categories of knowledge which it authorized and made available” (Asad, 29). But for Asad, there can be no transhistorical definition of religion. Variations in the historical relationships between power and knowledge are such that the search for a universal definition of religion constitutes, for Asad, a pointless exercise. Asad argues “that there cannot be a universal definition of religion, not only because its constituent elements and relationships are historically specific, but because that definition is itself the historical product of discursive processes” (Asad, 29). Any attempt to produce a tranhistorical definition of religion therefore constitutes a senseless denial of the historical specificity of religious phenomena.
The modern anthropological focus on religion as a distinct category of human behavior carries with it the implicit assumption that religion is “a distinctive space of human practice and belief which cannot be reduced to any other” (Asad, 27). For Asad, this irreducibility suggests that religion contains an “autonomous essence – not to be confused with the essence of science, or of politics, or of common sense” (Asad, 28). Furthermore, this understanding of religion as a transhistorical essence has been the result of a specifically Western tendency to remove the religious discourse from the political arena: “the theoretical search for an essence of religion invites us to separate it conceptually from the domain of power” (Asad, 29). But for Asad, this theoretical disposition is historically traceable to Christianity and should therefore be understood as being distinctively Christian. Our understanding of various phenomena deemed “religious” is largely a product of specifically Christian attempts to understand them: “the entire phenomenon is to be seen in large measure in the context of Christian attempts to achieve a coherence in doctrines and practices, rules and regulation” (Asad, 29).
Asad cites the early modern European construction of Natural Religion as a case in point. For Asad, Natural Religion, understood as “a shift in attention (…) from God’s words to God’s works” whereby “’Nature’ became the real space of divine writing” (Asad, 41), “was a crucial step in the formation of the modern concept of religious belief, experience, practice” (Asad, 41). Indeed, for Asad, Natural Religion constituted the first attempt at a universal definition of religion, a definition which happened to emphasized the concept of belief: “This emphasis on belief meant that henceforth religion could be conceived as a set of propositions to which believers gave assent, and which could therefore be judged and compared as between different religions and as against natural science” (Asad, 41). Furthermore, Asad points out that the concept of belief at the base of theoretical and comparative studies in religion is a fundamentally Christian one. The Christian church has therefore not had a small part to play in the construction of Natural Religion and the subsequent universal category “religion”: “it is preeminently the Christian church that has occupied itself with identifying, cultivating, and testing belief as a verbalizable inner condition of true religion” (Asad, 48).
For Asad then, the historical and anthropological construction of the category religion with its transhistorical essence must be understood in terms of its inherent Christianity. The universal definition of religion is more Christian than universal. For Asad, the pursuit of such a universal definition is at best a theoretically unreasonable project, and at worst an attempt to impose fundamentally Christian ideas on peoples of other traditions.
 Talal Asad, Genealogies of religion : Discipline and Reasons of Power in Christianity and Islam (Baltimore : The John Hopkins U.P., 1993).