A sound understanding of human history, development, psychology, etc leads inescapably to the conclusion that human civilisation is largely built on a foundation of cults.

Sometimes, a cult is able to grow and spread enough to become a new culture.

Some cults are jealous and demand the entirety of their followers' allegiance. Examples: Christianity, Islam, Communism, various Silicon Valley startups, certain Free-Marketism sects. [0] Others are more tolerant, and their followers can comfortably belong to several cults at the same time. Examples: Hinduism, Buddhism, Democracy, Existentialism, CrossFit, particular universities, gardening, the study of abstract mathematics, and sports clubs.

Yuval Noah Harari defines a religion as: a system of human norms and values that is founded on a belief in a superhuman order. [1]

I agree. I would also use this definition for "cult". However, I'd like to take this a step further: A healthy cult requires its followers to make regular sacrifices to demonstrate their allegiance to the cult.

Why?

Because healthy cults, with sacrificial rituals, solve the problem of establishing trust.

A sacrifice is an "honest signal". It is costly to its maker in some way. Individuals can't afford to make honest signals of allegiance to all the available cults, so the ones that they do make convey reliable information about their group affiliation.

When the members of a cult know that they have all bound themselves (by honest signals and opportunity cost) to the cult, a basis for trust exists, and complex cooperation can take place. Trade, war, construction, food storage, marriage, raising children, etc. [2]

Human existence depends so strongly on group cooperation that, practically speaking, cults are an absolute necessity. Without them, we atomise into individuals, and our societies disintegrate. We become dust in the wind. Our environment becomes chaotic, and we cease to be able to raise children. [3]

Other people, who have not made the same sacrifices, have the option to defect from the complex systems of cooperation, with nasty consequences for everyone else. This is why strangers / travellers / outlanders / newcomers are usually viewed with suspicion.

The fundamental political question is "Which gods do you sacrifice to?" i.e. "What do you spend your surplus resources / time / attention on? Do we belong to the same cult(s)? Can we trust each other enough to work together?".

Sometimes, particularly in times of economic / political stress, cult followers compete to sacrifice non-surplus resources (i.e. resources that they need for their own survival) to the reigning cult in order to demonstrate their loyalty. Those who stop first immediately become officially-sanctioned sacrifices themselves ("heretics" / "enemies of the people"). Most followers cannot afford to keep this up for very long - they run out of resources and die (or leave the cult, if they can). I think this explains why so many people died in the 20th State Communism cults. They had to keep sacrificing beyond their capability, and couldn't escape the cult's geographical control. "Comrades, the Communist utopia has not arrived only because we have not yet made enough sacrifices!". (Relevant: The War Continues)

Some cults develop sacrificial rituals that most people find abhorrent, due to constraints imposed by human biology. For example, the Romans and the Greeks were disgusted by the Carthaginian practice of sacrificing children to Moloch.

You already belong to at least one cult (else you would not have survived long enough to read this article). It might be worth identifying exactly which cult (or cults) you belong to, and thinking about how well that cult is doing in the current environment. Is it growing or shrinking in influence and effectiveness? Do the actions of the cult's followers lead to useful results?

The metaphysical content of a cult can vary quite a bit. It will make various claims about Existence. [4] Some of these claims will be reasonable. Others will be unreasonable - these are useful because they are a barrier to entry that prevents new people from entering into the cult too easily. If new people can easily join, some of them will join only for a little while, and then defect i.e. they will pillage the cult's stored social value and leave.

If the cult's worldview becomes too out-of-sync with reality, then its followers begin to suffer (because their actions in the world become less and less effective), and it begins to diminish in importance and influence. Other cults begin to grow at its expense, acquiring its mental / physical / economic territory.

The real test of the value of a cult's worldview is pragmatic: How effectively do its followers operate in the world? How powerful is the cult?