Religions are theories about the meaning of life. Commonly they have three interwoven elements: a morality, a theology and a feeling of ecstasy.
Some sort of morality, or code of conduct is a pre-requisite of the success of an intelligent social animal with a long period of youth and adolescence. Unless there are rules of behaviour that are widely obeyed it is difficult for communal activities to take place or for the next generation to be brought up. The precise form of the rules does not matter too much but they need to include a concept of group loyalty, and precepts as to individual relationships and the regulation of sexual matters.
Behaviour which is to the advantage of the group is not always to the advantage of an, individual when rationally analysed. It is because the rational analysis or even pseudorational analysis, in both of which man is versed, might cause the rules to be broken to an unacceptable extent that it is very useful to be able to tie them to the supra-human sanction of a religion.
Rules that are simply a biological convenience thus come to be inextricably involved with particular theologies in a relationship that is sometimes so clearly rationally indefensible that its existence may seem to damage the theology. Why, for example, should the truth of particular mannerisms be related to the number of wives appropriate to a male, however important this may be to the local group organisation?
The critical strength that a morality needs to have to ensure the continued existence of a group depends on how near the group is to the borderline of survival; provided the group morality keeps at least up to this critical strength, a good deal of failing from the optimum code of behaviour is tolerable. If one’s society is nourished by North Sea oil it can, if desired, afford to emulate Sodom and Gomorrah, but it cannot do so if it is based on goats nibbling at thorn scrub. There is a sort of regulating mechanism in that when a group is outstandingly successful the rules relax, and this relaxation tends to a decline of a group. In other words too much luxury tends to lead to decadence.