<p>The thesis defended in this paper is that philosophy’s knowledge of its history is not merely illuminating or educational but <i>indispensable</i> for its progress and pursuit of truth. It is argued, first, that philosophy can only sufficiently appreciate the meaning and significance of its present concepts and problems if it has at its disposal tools for critical evaluation, including tools that only a knowledge of its history can supply. Philosophy’s past, in other words, contains crucial clues to its present self-understanding and practice. Second, philosophy must know its history if it is to dispense with a certain illusion about itself. This is the illusion that truly original ideas <i>have</i> no history but are instead generated ex nihilo from the thinker who has successfully left her past behind. The paper concludes with a brief discussion of two philosophers who very much appreciated these reasons for why philosophy needs to know its history: Nietzsche and Hegel.</p>