This article focuses on the problem of how Gustav Teichmüller understands the relationship between the history of philosophy and systematic or speculative philosophy. Is the history of philosophy (and ultimately the history of all thought) merely a broom closet full of arguments, or does it play a substantive and constitutive role for contemporary philosophy and systematic thought? In the course of the article, it becomes evident that Teichmüller’s treatment of this issue is remarkable in many respects and relatively topical even today.