2013 marks the fiftieth anniversary of the publication of Martin Luther King’s ‘Letter from Birmingham City Jail’. Written during the height of the struggle for African-American civil rights in the United States, the document (an essay written in the form of an open letter) represents a powerful philosophical and theological treatise about social justice and the nature of social and political change. The letter addresses a number of important themes that remain relevant today for community and political activists concerned with social justice. The article briefly highlights three key issues and their significance in terms of a political understanding of social and political change. First, the nature of a so-called civil society; second, the role of the ‘outsider’ as political agitator; and third, the significance and necessity of tension in promoting social justice.