A book that ranges across five thousand years stands, at every step, upon the labour of others, and my debts are beyond proper counting.
To the scholars whose lifetimes in the archives made this synthesis possible I owe the greatest of them. Any history of ancient bondage must build upon the foundational work of Moses Finley, who taught us to distinguish the slave society from the society that merely has slaves; of Orlando Patterson, whose conception of slavery as a kind of social death runs throughout these pages; and of Keith Bradley, Keith Hopkins, Walter Scheidel, and Kyle Harper, among many others, whose patient researches into the Roman world I have drawn upon constantly. For the long afterlife of the institution I am indebted to the historians of serfdom, of the medieval and Islamic trades, and of the Atlantic crossing, and to the scholars whose painstaking work at last allowed that final horror to be counted.
I owe a different and deeper debt to the few of the enslaved who left us their own words - to Equiano, to Douglass, to the writers of the slave narratives - who proved, simply by speaking, what the silence of the ancient record can only imply.
To the friends who read these chapters in draft, and to those nearest me, who bore the long preoccupation with patience and with love, my thanks are quieter, and greater, than any page can hold.