This is the first dissertation written by an African slave. He was brought to Holland by his owner, freed, and educated at the University of Leiden with grants from wealthy burghers. Thereafter he returned to Guinea as a missionary. His analysis presents a sweeping intellectual genealogy of Western thought on the issue of slavery. It begins by discussing the authors of antiquity, using Seneca, Horace, and Justinian to show that slavery violated the principles of natural freedom and equality, and rebutting Aristotle's doctrine of natural slavery. Capitein concluded from Genesis that slavery entered the world as injustice to all peoples, but argued that the freedom promised in the Gospels was spiritual, not corporeal, and therefore had no civic consequences. The book represents the first scholarly work by an African on slavery, connecting Western thought and African experience.