This is a book about labour systems that were unfree. What made them "unfree"? How did "free" labour evolve? Part 1 presents a history of those "unfree" systems in turn, highlighting what made them unconscionable by modern standards. Part 2 moves from a history of institutions and practices to a history of the ideas that underpinned and sought to justify extreme examples of cruelty and oppression. How and why did the institutions and the ideas that explained them evolve? What role did the modern idea of freedom play in the evolution of a labour system based on a contract between equals? This introduction to labour history and the ideas behind it, is a story of one way in in which our world was changed.