Philosophers from Europe and colonial America engaged in heated debates about the morality of slavery in the sixteenth and seventeenth centuries, and these debates provide insights into the roots of modern racism. Julia Jorati explores the philosophical ideas, theories, and arguments that are central to early modern discussions of slavery. Some texts explicitly examine the morality of the transatlantic slave trade or of the enslavement of indigenous people in the Americas; others discuss slavery in predominantly theoretical ways. Based on these texts, Jorati shows that race and slavery came to be closely associated in this period. This association was often made through an endorsement of the theory of natural slavery: Black and indigenous people were commonly viewed as natural slaves, or naturally destined for slavery. The theory that some people are natural slaves also features prominently in theoretical discussions of slavery, and many philosophers in the sixteenth and seventeenth centuries embraced versions of it. Jorati surveys a wide range of historical material, from the views of Thomas Hobbes, John Locke, and Gottfried Wilhelm Leibniz, to many less widely studied philosophers like Gabrielle Suchon, Morgan Godwyn, and Epifanio de Moirans. Jorati's volume, along with its companion Slavery and Race: Philosophical Debates in the Eighteenth Century, illustrates the significance and philosophical sophistication of early modern debates about slavery, and serves as a valuable resource for scholars, instructors, and students who are curious about this widely neglected topic.