“Religion has no accepted definition.” <– That’s one of the first and most common refrains that you’ll hear in any religious studies class, but it’s been useful for me to use a functionalist perspective: a narrative fabric that undergirds the mores of its community[1].
It comes in a vast variety of textures, but always upholds some normative structure by binding together some set of values. Religion is both fluid and hollow: if the contents therein are shifted or transform (or disappear!), the cult will follow suit. Thus, there are no vestigial religions; any such examples are ‘dead’. Such an account denies autonomy from religion not entirely fairly, but I think it serves well enough.
Secularism has been rising in the modern world without signs of stopping, but with this understanding one might question the premises of that data. Until we reach collective omniscience by means of pure reason, there will always be epistemic negative space within which religiosity can exist. Until every sentient community has dispersed, there will always be need of ethical apologia.
- note that this semantic is almost meaninglessly broad, as it encompasses everything from free market economics to Homerian myth. this is a feature and not a bug.