This book investigates the philosophical path that took Heidegger through phenomenology to the question of the meaning of Being, from his initial encounter with Husserl's texts in phenomenology in 1909 to his definition of phenomenology as 'fundamental ontology' in Being and Time (1927). It explains how Heidegger comes to the conclusion, around 1919, that this question had been left 'unthought' by Husserl in phenomenology and phenomenological research and why he had go in search of an alternative method of enquiry to Husserl's in order to retrieve this issue for phenomenology. The study identifies three methods of enquiry that Heidegger uses and that are of most relevance to his effort of 'raising anew' the question of the meaning of Being in phenomenology. These are: Dilthey's historical-hermeneutic method, Kierkegaard's existentialist method, and Schleiermacher's biblical-hermeneutic method. It also investigates the centrality of Heidegger's existential-phenomenological analysis of 'being-for-death' in Being and Time in terms of its unique contribution to philosophy and phenomenological research and as a radical immanent philosophical critique of Husserl's version of post-Kantian transcendental idealism defended in Ideas I (1913).