Vampires are generally considered as evil in traditional lore. Most vampires love to drink human blood, however Cullens do not. Though its bit difficult for them to avoid their craving, nevertheless the mission of Carlisle to avoid taking part in evil acts is a strong will enough that helps them to abstain from desiring for human blood. So, overriding this urge is obviously difficult for Edward when he finds delicious smell of Bella’s blood. His conscious desire is never involve in evil act and never be a monster relentlessly conflicts with unconscious push for her blood. Thus, overall in this novel, good vs. bad theme is about an individual decision, rather than an irrepressible fate.