What may not be expected in a country of eternal light

Some keep the sabbath in surplice - i just wear my wings - and instead of tolling the bell, for church, - our little sexton - sings

London includes a quote about john thornton as he is observing hal attempt to motivate the exhausted dogs "it was idle, he knew, to get between a fool and his folly". if the word "idle" is defined as "of no real worth, importance, or significance", what does this statement mean with regard to hal? who is the fool? what is hal's folly? why would john thornton think it of no real worth or useless to intervene?

Based on this excerpt the authors are mostly likely to attempt to answer which question?