Although Bernard Lonergan is known primarily for his cognitional theory and theological methodology, he long sought to formulate a modern philosophy of history free of progressive and Marxist biases. Yet he never addressed this in any single work, and his reflections on the subject are scattered in various writings. In this pioneering work, Thomas McPartland shows how Lonergan’s overall philosophical position offers a fresh and comprehensive basis for considering historiography. Taking Lonergan’s philosophy of historical existence into the realm of an epistemological philosophy of history, he demonstrates how the philosopher’s approach builds on the actual performance of historians and, as a result, integrates the insights of historical specialists into a framework of functional complementarity. McPartland draws on all of Lonergan’s philosophical writing—as well as on the vast literature of historiography—to detail Lonergan’s notions of historical method, historical objectivity, and historical knowledge. Along the way, he explains what Lonergan means by hermeneutics; by historical description, explanation, ideal-types, and narrative; by evaluative and dialectical analyses; and how these elements are all functionally related to each other. He also delineates the defining features of psychohistory, cultural history, intellectual history, history of ideas, and history of philosophy, indicating how these disciplines play complementary roles in the critical encounter with the past. Ultimately, McPartland argues that Lonergan has established the principles of a historical discipline—the history of consciousness—that weaves together a philosophy of consciousness with rigorous historical research to grasp long-term trends resulting from “differentiations of consciousness.” His work offers a distinct perspective on historical method that takes historical objectivity seriously while providing new insight into the thought of this important philosopher.