From his origins in Phenomenology, Heidegger undertook methodological changes which thematize pre-theoretical life and lead to the hermeneutics of Dasein. This process created tensions with Husserl that affected both the theoretical and the personal dimensions. This article studies this turning point, showing its early origins and focusing on the contributions of the Introduction to phenomenological research course, from the winter semester of 1923/1924. This text presents relevant aspects in order to understand the way in which Heidegger redefined the notion of phenomenology, the strategy to object the husserlian position because of its cartesianism, and the tension between consciousness and facticity. This exploration will offer elements to comprehend the points that would lead to the friction between both philosophers in a manner that marked out contemporary thinking.