In the 1790s, many post-Kantian German philosophers attempted to lay a new foundation for the historiography of philosophy. Earlier works on the topic, they argued, made out mere aggregates of disconnected sources and allowed for no understanding of the overarching, rule-bound nature of reason’s historical development. This error was to be amended by applying the insights of Kant’s Critique of Pure Reason, which the post-Kantians believed to offer a universally valid and unbiased method for approaching the philosophical thought of the past.

I argue that this historiographic strain in post-Kantian thought is often misunderstood. It is frequently described from a presentist viewpoint that makes it appear as merely a tendentious apology for critical philosophy. In this dissertation, I approach post-Kantian historiography of philosophy in a different way, namely, by situating it in the historically specific situation in which it arose. First, I attempt to make sense of post-Kantian theories and practices of the history of philosophy by relating them to earlier traditions. Second, I trace the development of post-Kantian historiography during its most vigorous period until the time it started tobe challenged by other, new historical methods and ideals around the middle of the 19th century.

A main result of my study is that the post-Kantians posited reason as such as the subject of the history of philosophy. This subject transcended both particular individual philosophers and particular schools of thought. To achieve this narrative of reason’s historical development, the post-Kantians established what I refer to as a “depth model”. The task of the historian was, in their view, to reach from the outer expression of historical philosophies to their rational essence, from their letter to their spirit. This ambition led to a number of new historiographical challenges. It forced the post-Kantians to reconsider the role of biographies in the history of philosophy, the geographical scope of this history, and the relation between history’s temporality and reason’s eternity. Throughout my examination, I account for all of these issues and how the post-Kantians attempted to resolve them. I claim that their approach in general can be described in terms of performative concept work, i.e., a use of concepts that was made possible by certain already-given frameworks of understanding, but that simultaneously transformed these frameworks and gave them a set of new meanings. Ultimately, I argue, the period led to a wholly new concept of “the history of philosophy” as such.