This introductory chapter sets out the book's purpose, which is to explore the similar forms, themes, and functions that tend to recur in the prison writing of European intellectuals. The book juxtaposes different pairs of writers across national and period boundaries, from late antiquity to the late twentieth century. Although the experience of different centuries and regimes varies greatly and there is no single category of space implied—all the subjects of this book suffered involuntary confinement in different conditions—being a prisoner or captive in any period means being cut off and kept apart from the continuities of normal life, however that was defined. Many of these prisoners remain well known—Boethius, Thomas More, John Bunyan, Marie-Jeanne Roland, Oscar Wilde, Antonio Gramsci, Dietrich Bonhoeffer, Anne Frank, and Primo Levi. Yet their different kinds of writing in captivity have never been read alongside each other so closely and extensively as specific responses to their various kinds of imprisonment.