What is the theme in Pedagogy of the Oppressed by Paulo Freire?

The main theme of Freire's book is oppression, the state of society that causes one class of people to remain entrenched in poverty while another class of people enjoys the benefits of the lower class's labor. Freire believes that oppression is an act of violence by the oppressors, who violate the oppressed by suppressing their humanity and making them impotent to think and act. The oppressed become part of a system that keeps them from advancing as human beings or acting on the world according to their will.