Ludwig Wittgenstein and Martin Heidegger are widely recognized as two of the most infl uential and important philosophers of the twentieth century. Born into German-speaking families in the same year, each emerged as the star pupil and anointed successor of the leading fi gure in their respective traditions: Bertrand Russell with Wittgenstein in analytic philosophy and Edmund Husserl with Heidegger in phenomenology. Russell and Husserl expected their protégés to continue the work they had begun, but Wittgenstein’s Tractatus Logico-Philosophicus and Heidegger’s Being and Time radically questioned and cast serious doubt on that work. Yet Wittgenstein and Heidegger did not stop there. After turning away from their mentors’ teachings, they both went on to revise their own earlier thought. And although the extent of this revision is open to debate in each case, both clearly came to view their later thought as a response to-and criticism of-their more youthful philosophical endeavors.