Introduction to Phenomenological Research, volume 17 of MartinHeidegger's Gesamtausgabe, contains his first lectures given at Marburg in thewinter semester of 1923--1924. In these lectures, Heidegger introduces the notion ofphenomenology by tracing it back to Aristotle's treatments of phainomenon and logos.This extensive commentary on Aristotle is an important addition to Heidegger'songoing interpretations which accompany his thinking during the period leading up toBeing and Time. Additionally, these lectures develop critical differences betweenHeidegger's phenomenology and that of Descartes and Husserl and elaborate questionsof facticity, everydayness, and flight from existence that are central in his laterwork. Here, Heidegger dismantles the history of ontology and charts a new course forphenomenology by defining and distinguishing his own methods.