Virtue could see to do what Virtue would By her own radiant light, though sun and moon Were in the flat sea sunk. And Wisdom's self Oft seeks to sweet retired solitude, Where with her best nurse contemplation She plumes her feathers, and lets grow her wings That in the various bustle of resort Were all too ruffl'd, and sometimes impair'd. He that has light within his own clear breast May sit i'the centre, and enjoy bright day, But he that hides a dark soul, and foul thoughts Benighted walks under the midday sun; Himself is his own dungeon.

-Milton,John
  Comus,  A Mask, l.372^83.