“Religion” is a category that cannot be defined. There are certainly definitions out there, but there are several problems undermining every single one. From a theoretical point of view, there’s the fallacy underlying dictionary definitions that assumes terms and concepts develop based on underlying conceptual structures. According to these assumptions, categories develop from and are governed by sets of necessary and sufficient features. The necessary ones are necessary for inclusion; the sufficient ones are sufficient to distinguish the members of the category from other categories. A definition is generally the smallest set of features that separates the category from all others. For example, a “bird” can be defined as a (1) feathered (2) vertebrate (3) animal. Those three features are necessary for inclusion and sufficient for distinction.
This works for birds, but it does not work for most categories, and particularly conceptual constructs. Take “furniture,” for instance. Try to reduce everything you refer to as “furniture” down to necessary and sufficient features without including numerous things that aren’t really furniture. Definitions of religion that try to distill the concept down to necessary and sufficient features do one of two things: (1) they choose features that do not include all the phenomena widely called religion, or (2) they choose features that are so broad that they include traditionally non-religious institutions. Regarding the first, many definitions include belief in supernatural beings as central to religion, but many traditions long referred to as religions do not assert supernatural beings, which makes that an inaccurate feature. Regarding the second, other definitions use features that are far too broad, like concerns with an afterlife, the transcendent, or ritual. These features would include numerous institutions not considered “religions.” The fact is that the concept does not have boundaries. Human language is not focused on boundaries of concepts, but on their centers. Boundaries are fuzzy and unclear until a need arises to draw them, and at that point rhetorical expediency is usually what determines them. No boundaries can successfully be drawn around the concept of religion in any way approaching objectivity or empiricism.
The next problem is that the entire concept of religion itself was created during the Enlightenment to serve Western structurings of values and power, and particularly colonialism. The original Latin term religio referred to any social or ethical responsibility or obligation, usually involving ritual or the performance of some task. Over time it began to refer to obligations to deities. When it was adopted into developing Christian worldviews, it referred to the monastic orders. Each order constituted a different “religio” within Christianity.
When the Reformation brought increased power and influence to the separate offshoots and movements within Christianity, it raised concerns for how to understand their relationship to each other, to Jewish and Muslim cultures, as well as to the new cultures that were increasingly coming under the scrutiny of Westerners. This began the internalization and privatization of “religion” as a compulsion to the divine. Religion was a universal and innate orientation to God (it was asserted to be monotheistic) that resulted in different cultural mores and practices as it was filtered through the fallen minds and practices of the different cultures of the world.
Protestant Christianity was considered the most pure expression of “religion” (it was Protestants doing the considering). Catholicism was considered just as depraved and corrupt as other non-Christian cultures. The term paganopapism began to be used to equate Catholic priestly practices with paganism, precisely in the service of this view of “religion” as an internal cognitive phenomenon, rather than obligatory practices and rituals. As Protestant Christianity continued to fracture and multiply the available vehicles for salvation, bickering and infighting became quite a concern, particularly for the state. Salvation became more about propositions than about institutions, which divided up the available channels, and we finally had plural “religions.”
The discovery of and increased exposure to different cultures required a rubric under which they could all be situated, and Protestant notions of religion were used as a framework for understanding their worldviews and their practices. We have scriptures, so we looked for their scriptures. We have beliefs about deity, so we looked for their beliefs about deity. This influenced the way other cultures thought about themselves, their practices, and their relationship to us. As an example, Ghandi first read the Gita in an English translation in the UK. The impact of this scripturalization and interiorization of religion on other cultures would be difficult to overstate. It certainly facilitated and rationalized European colonialism, and today’s definitions, directly descended from those of the Enlightenment, continue to facilitate the cultural and ideological imperialism of both religious and non-religious groups.
For these and a number of other reasons, the notion that “religion” is a phenomenon that can be empirical distinguished from others is suspect. To speak of “religion” in antiquity is even more problematic, as there’s no evidence whatsoever that anyone ever organized their institutions or ideas according to that rubric. Distinguishing religion from culture, politics, ethnicity, etc., generally serves someone’s structuring of power, and for that reason alone, we ought to be careful about it. The fact that those distinctions also tend to prioritize belief over and against practice and other relationships raises further concerns with the usefulness of the category.
Here are some publications for further research:
W. C. Smith, The Meaning and End of Religion
Fitzgerald, The Ideology of Religious Studies
J. Z. Smith, “Religion, Religions, Religious”
Asad, Genealogies of Religion
Masuzawa, The Invention of World Religions
Boyer, The Fracture of an Illusion
Cavanaugh, The Myth of Religious Violence