An Enemy of the People is one long power struggle. Whether it's the intense sibling rivalry at the core of the play, or the petty maneuverings of the play's secondary characters, everybody is constantly battling for turf. Many of the characters spend their time in efforts to gain control over other people. Interestingly, by the end the play's protagonist, Dr. Stockmann, comes to the conclusion that a person has the most strength when his power is contained wholly within himself. He declares, "the strongest man in the world is the man who stands alone" (5.310).
Those in power control public opinion.
The Doctor's actions show the power of one man in a corrupt society.