Men thought them out together; nay, whole ages of living and thinking together have gone to make them what they are.

So a social method is needed to explain them.
The religion of a savage is part of his custom; nay, rather, it is his whole custom so far as it appears sacred--so far as it coerces him by way of his imagination.

Between him and the unknown stands nothing but his custom.

It is his all-in-all, his stand-by, his faith and his hope.

Being thus the sole source of his confidence, his custom, so far as his imagination plays about it, becomes his "luck." We may say that any and every custom, in so far as it is regarded as lucky, is a religious rite.
Hence the conservatism inherent in religion.