Although Jesuit contributions to European expansion in the early modern period have attracted considerable scholarly interest, the legacy of José de Acosta (1540–1600) is still defined by his contributions to natural history. The Theologian and the Empire presents a new biography of Acosta, focused on his participation in colonial and imperial politics. The most important Jesuit active in the Americas in the sixteenth century, Acosta was fundamentally a political operator. His actions on both sides of the Atlantic informed both Peruvian colonial life and the Jesuit order at the dawn of the seventeenth century.