It comes about as rational actors make informed choices between realistic alternative lifepaths, always taking responsibility for the consequences that those choices will have on their own cumulative life stories […]

So a law of nature which said, say, that Ravenhood is causally linked with blackness would entail both All ravens are black and All non-black things are non-ravens, but would not entail a law linking non-blackness with non-ravenhood.

For example, caregiver reactions may be quite different for a highly irritable, highly soothable child, as compared to an equally highly irritable child who is not soothable.

Note the two-horse whippletree on the beam at the lower left. (A whippletree, of which this is the simplest possible, balances the load on the animals.)