Many works describe themselves as "genealogies", but it is far from clear that this term picks out a single kind of historical-philosophical project. This paper examines the role historical investigation plays in Bernard Williams’s Truth and Truthfulness and contrasts it with the role of history in Nietzsche’s genealogy. Williams himself saw the philosophical approach in Truth and Truthfulness as an appropriation of Nietzsche’s historical method. However, the role of historical investigation in their respective works is in fact importantly different. Moreover, a key function of history in Nietzschean genealogy is to question assumptions that are required for history to play the role it does in Williams’s project. Considering these differences can help us understand their respective projects as well as illustrate different ways historical investigation can be integrated into philosophical reflection.