Quote from : The Crucible Book

[W]e conceive the Devil as a necessary part of a respectable view of cosmology. Ours is a divided empire in which certain ideas and emotions and actions are of God, and their opposites are of Lucifer. It is as impossible for most men to conceive of a morality without sin as of an earth without 'sky'. Since 1692 a great but superficial change has wiped out God's beard and the Devil's horns, but the world is still gripped between two diametrically opposed absolutes. The concept of unity, in which positive and negative are attributes of the same force, in which good and evil are relative, ever-changing, and always joined to the same phenomenon - such a concept is still reserved to the physical sciences and to the few who have grasped the history of ideas.