I am attempting to classify the various explanations of the existence of religion, so chime in the comments.
They are:
1. The intentionality explanation
Human beings are agents and highly adapted to social life. As a result, our cognition tends to take what Dennett calls the “intentional stance”. That is, we ascribe intentions to non-agent processes. In earlier terminology, this was called “anthropomorphism”, or the treating of non-human things as if they were human.
One will often read explanations of religion as the anthropomorphisation of natural processes like spring, rain, thunder, flood, storms, and so on. When the rain washes away your village, it makes more “sense” to say that the rain god was angry with the village, because that is an explanatory schema that we have imprinted in our native cognition. Hence, natural processes became personified (or not personified but abstracted, as in the early Roman rural deities, the numina, which were forces rather than agents).
2 The ancestor worship explanation
All rural and village based religions place high value on ancestors. Forebears were reverenced after their death, and eventually ended up as figures who in some manner still had a place in social behaviours. Ideas of “honour” relied in large part on this (one had to honour one’s ancestors by behaving in ways they would approve of).
This ancestor based explanation depends on the role of cultural transmission, both of knowledge (heroic figures like Prometheus, who stole fire from the gods, and Tubal-Cain in Genesis 4, who is the ancestor of those who made bronze and iron tools), and of social groupings (again, Genesis 4, 5, 10 and 11 mention these figures). Founders of cities and peoples are especially mythical (Romulus and Remus, Dido of Carthage, Nimrod, founder of the Mesopotamian civilisation).
These individuals may or may not have lived or done what they are remembered and worshipped for, but they act as social glue for subsequent cultures, as social myths that serve to cohere the state or culture. Often they justify, in virtue of their prowess as warriors or strategists, the dominance of the society over others.
In time, these mythical heroes become deities or children of deities, in an attempt to further explain their achievements and position of importance.
3. The existential explanation
A common explanation is the “fear of death” or “fear of lack of control” over the powers of the world. Here, the idea is that a deity promises release from death, or control over events, that one cannot achieve individually or as a social group, particularly when the group is less powerful than rival nations.
In many cases, religions actually do not offer either release from death or control over the course of events, so much as they validate those who die or suffer. If you are doing the dying or the suffering of fates slings and arrows at the plan of a benign and powerful deity, then the suffering is less tragic and brings honour. In particular religions that lack an afterlife or have it as a shadowy existence like the Roman Elysian Fields offer that one’s family and name will be granted honour, if, for example, you die in war. As Horace said, dulce et decorum est pro patria mori (It is fit and proper to die for one’s homeland). While this makes sense from the view of the state, it doesn’t from the view of the warrior and his (usually his) family; so a religious justification will serve to both enforce submission and sacrifice for the homeland, and to ensure that those left behind gain in social standing from it.
4. The memetic explanation
This is also from Daniel Dennett: religion is a “mind virus” that “infects” human brains and makes use of their capacities and resources to propagate itself. Such viral infestations of our mental contents are called “memes”. It follows that the “evolutionary interests” of these memes and those of the human individuals that act as their “host organism” are divergent in many cases. This view is, in effect, a side effect of our ability to pass on cultural information, but the religious memes are cheaters; they take advantage of our cultural skills to get themselves replicated, evolving more and more tricky ways to deceive and cheat our genetic interests.
A point of interest with this view is what it is that memes are adapting to. At the least they are adapting to our cognitive and sociocultural properties and propensities. They may also need to adapt to the cultures in which they are passed on (see next item).
5. Social cohesion
This is very like the ancestor worship explanation. It posits that anything that permits greater social cohesion will tend to improve the fitness of the group overall, and so improve the individual fitness of those who are part of the group, on average. Hence, religion, which serves both to mark those who are inside the group and can expect to be treated with reciprocal altruism and to mark those who are outside the group and are competitors to whom no loyalty is owed, is beneficial in an evolutionary sense.
In this case, the evolution of societies is roughly equivalent to the evolution of religions. The meme account has memes of religion adapting to the cultures in which they are passed on (so that first century, third century and 21st century religions are very different even when there is direct continuity between them). The social cohesion account has religion adapting to the competition between social groups.
6. The psychopathology explanation
Religious experience is also adduced as a source of religion. Ranging from “feelings of the numinous” and “awe” to explanations of epilepsy and schizophrenia for shamanism, these explanations go back to the nineteenth century.
