Costly commitments only build solidarity when backed by supernatural monitoring

Evidence

Interestingly, the number of costly requirements did not predict longevity for secular communes. This means that there is something distinctive about religious groups that makes costly behaviors a potent source of social solidarity. There could be several reasons why religious but not secular communes benefit from imposition of costly behaviors, but supernatural monitoring ought to be one key factor that galvanizes and amplifies social solidarity if it is backed up by extravagant displays of faith. — Norenzayan, Ara, Big gods - how religion transformed…, 352

Categorization

• XREF: Core link to the reader’s stated project: the costly requirement is effective only in religious groups precisely because of the perceived omniscient gaze — this is Norenzayan’s Big God mechanism sharpened by the cost dimension.
• QUESTION: Why exactly do costly demands fail to build solidarity in secular communes but succeed in religious ones? The book names supernatural monitoring as ‘one key factor’ — worth pinning down what the other candidate factors are.