It is obvious that Freek tragedy,especially Aristotle's hamartia has greatly influenced Hardy's writing and there is a serious vein of tragedy throughout the novel.
In chapter thirteen, Aristotle outlines an ideal of the central character of tragedy, the so-called tragic hero, and identifies the source of the character's downfall with something called hamartia.
This reversal is caused not by depravity, which would not be tragic as it would not allow for any philanthropic sentiment like pity, but by error, hamartia.