Considering the issue of control, how much control does Dr. Jekyll have over his actions/decisions - the good/the evil?
In Robert Louis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde, the question of control, or more specifically the lack of control, is an important consideration. As Mr. Hyde, Dr. Jekyll exercises little if any control over the actions of his alter ego. This fact both excites and scares Dr. Jekyll. A product of a repressive Victorian society, Dr. Jekyll sees the images and thoughts he has as Mr. Hyde as a way of escaping the restrictions of his everyday life.
This being said, this does imply that Dr. Jekyll could control the actions of Mr. Hyde if he wished to do so. This apparent ability to control his alter ego wanes over the course of the story, making it Dr. Jekyll's control over Mr. Hyde's actions/decisions less and less firm. In the end, Mr. Hyde outstrips Dr. Jekyll's control, so much so that Mr. Hyde must die.
It is in this action that Stevenson's central theme - the dangerous duality that resides in mankind - becomes most apparent. The duality of good versus evil, when applied to Dr. Jekyll's attempts to assert control over his darker half, appears more as a struggle between two impulses: the impulse to give into one's darker thoughts and the impulse to repress them. Ultimately, The Strange Case of Dr. Jekyll and Mr. Hyde serves to warn humanity of the possibility (and perhaps the inevitability) of evil resisting the repression of good. Good's "victory" over evil may decide the battle, but the war between good and evil is anything but decided.