Inspired both by debates about the origins of the modern ideology of race and also by controversy over the place of Ireland and the Irish in theories of empire in the early modern Atlantic world, this pathbreaking study argues that ethnic discourse among the elite in early modern Ireland was grounded firmly in the Renaissance Humanism and Aristotelianism which dominated all the European universities before the Enlightenment. Irish and English, Catholic and Protestant, all employed theories of human society based on Aristotle's Politics and the natural law of the medieval universities to construct or dismantle the categories of civility and barbarism. The elites operating in Ireland also shared common resources, taught in the universities, for arguing about the human body and its ability to transmit hereditary characteristics. Both in Ireland and elsewhere in Europe, these theories of human society and the human body underwent violent changes in the late seventeenth century under the impact of the early Enlightenment. These changes were vital to the development of race as we know it. Ian Campbell both interrogates neglected Latin-language sources in print and manuscript and re-interprets well-known writings by Richard Stanihurst, Edmund Spenser, and others to build an analysis of Irish Renaissance Humanism as a politically and ethnically relevant tradition densely intertwined with European intellectual life. Renaissance humanism and ethnicity before race will prove essential reading for students of race, the early modern European empires, and British and Irish history.