Full Idea
The four standard explanations given for religion are that it provides answer, that it gives comfort, that it makes for social order, and that it rests on mere superstition.
Gist of Idea
Religion gives answers, comforts, creates social order, and panders to superstition
Source
A.C. Grayling (What is Good? [2003], Ch.4)
Book Reference
Grayling,A.C.: 'What is Good? The Best Way to Live' [Phoenix 2003], p.83
A Reaction
All four of these could be correct, though the first and fourth would be incompatible if religion gives correct answers. Why religion begins might be not the same as the reason why it continues.