Cognitive Science of Religion for Dummies 1.0...

Image: Wikipedia

... in a nutshell, it all depends on agents & intentionality.

Agents are considered as the main force behind what happens in the natural world - and that’s a by-product of the way primates’ brain is hardwired to cope with their intense social life (e.g., if it’s raining, it’s because someone wanted it). For instance, when a storm is approaching male chimps might assume an aggressive stance towards the big rain-laden clouds coming, as if they’re just agents like them, who can be driven away by shouting at them or by throwing sticks or rocks at them.

Intentionality is the result of desires and beliefs which prompts an agent to do things and actions (i.e., eat, sleep, looking for a male/female, interact with another social agent, etc.).

Theory of Mind (ToM) is the ability to read the intentionality of other agents, in order to interact and attribute mental states (intentions, desires, beliefs, etc.) to those agents involved with us in the social environment.

So, if you are living in a natural environment surrounded by other agents, in the deep times of evolution you’re probably expected to develop a sort of mental hyper-active detection device for agents, just in order to stay alive: if you hear some noise in the bushes, and you think it’s the wind, but actually there’s a predator lying there and waiting for you, you become its meal!

However, if you decide to interpret that noise as the product of a hidden threat and you finally decide to run away, you’re safe, and you can pass your genes to next generations - even if there was no predator at all. Thus, ToM is not a perfect device, but evolution is not meant to be perfect, as it’s all about good enough solutions.

Now on for something different. Special agents are held responsible for patterns of natural and social events, which usually may have a personal or collective meaning (even though those patterns are the result of arbitrary and meaningless noise). Special agents such as ghosts, talking animals or deities break the ontological categories of our cognition in a way that rewards the spread of certain narratives. This happens thanks to some counter-intuitive features present in our communications. For example, a serpent that speaks breaks the normal biological expectations; this violation assigns a psychological human feature to that peculiar agent, and this makes that narrative more recognizable,  memorable and prone to social spread.
Special agents are also the aim of rituals in which a purported invisible agent is the recipient of a communication or an offer in which there might be no intelligible technical motivation or purpose - after all, some animal rituals also do play a certain functional role in sociality, but may have no explicit meaning at all. High levels of sensory pageantry (with particular music, foods, psychoactive substances, even tortures, etc.) characterizes the virtual presence of the special counterintuitive agent in a given ritual. This pattern may takes place once in a life time, and its effects are considered permanent. Repetitiveness is the mark of a second type of ritual, in which the passive patients (i.e., the human participants) are the main protagonists of the performance. This kind of ritual, which features a much lower degree of emotional involvement, must be routinely repeated.

Memory is involved in the further elaboration of rituals, which in turn is connected to specific political/social organization: episodic memory is involved in occasional or rare, emotionally arousing rituals (such as the rites of passage widespread in the world, or the baptism in Christian societies), and is inclined to produce very small groups in which everyone knows each other, typically with low levels of orthodoxy and no leadership. This is the imagistic mode of religiosity (it is not related to images at all!).

Semantic memory, instead, is typical of frequent ritual based on monotonous repetition (such as the Sunday mass), and tend to produce vast, expandable communities with loose strings (i.e., the participants might not know everyone involved elsewhere in the same creed), with higher levels of controlled orthodoxy and a strong leadership. This is the doctrinal mode of religiosity.

To cut a very long story short, these are the evolutionary basic roots that explain why people in the whole human history have shared beliefs in spirits, ghosts and deities as counterintuitive, invisible entities/agents. These bullet points also clarify why people have elaborated a whole lot of complicated rituals in order to get the attention of unreachable agents thought to be present in the natural world.