Robert Louis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde depicts a man torn between his "good" and "evil" self. This idea has been popularized in Gothic Romantic works (like Stevenson's text and Mary Shelley's Frankenstein). Gothic Romantic authors, when dealing with the doppelganger (a person's "twin"), play upon the idea that people possess both good and evil within themselves. While the amount of good and evil is unknown, everyone possesses the ability to be both good and evil.
A thesis statement which addresses the idea of good and evil within the text is as follows.
The dual nature of human mentality, symbolized by the evil of Mr. Hyde and the good of Dr. Jekyll, illustrates the battle which rages within an individual. Robert Lewis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde represents the battle between the intellectual and rational self and the irrational and animalistic self.