"Phenomenological Interpretations of Aristotle", the text of a lecture course presented at the University of Freiburg in the winter of 1921 and 1922, was first published in 1985 as volume 61 of Heidegger's collected works. Preceding Being and Time, the work shows Heidegger attempting, through the use of novel vocabulary, to find his personal philosophical voice. Heidegger takes up the task of defining philosophy and elaborates a unique discussion of "factical life," or concrete human life as it is lived in relation to the world, a relation he calls "caring." Heidegger's descriptions of the movement of life are original, striking, and unique to this lecture course. As he elaborates a phenomenology of factical life, Heidegger prepares readers for actual engagement in the work of phenomenology and introduces a phenomenological interpretation of Aristotle, one of the pivotal influences in the development of his philosophy. Important and detailed discussions of phenomenological research, philosophical definition, formal indication, the relationship between philosophy and the sciences, facticity, the surrounding world, questionability, and temporality emerge from this provocative text. In its very early articulation of Heidegger's thought, it will be an indispensable resource for scholars and students.