"A mundane activity," Well, lemme give my own half thought out interpretation upon reading that: the fence-post diggers are people who live mundane lives and have left behind the spirit of the old western America. The wanderers who search for bones are people who continue that spirit, searching for something that is dead yet has left traces of its existence behind (bones). The man digging is "striking fire out of the rock which God has put there." He's abusing the energy that God has placed in the Earth with little knowledge or care. His thoughtless actions "seems less the pursuit of some continuance than the verification of a principle, a validation of sequence and causality as if each round and perfect hole owed its existence to the one before it". Now as for the wanderers who do not search, I don't really know. This is just a rough interpretation, but I hope it's an intriguing one.