Le concept phenomenologique de phenomene chez Heidegger. 'Sein und Zeit' et les 'Marburger Vorlesungen' de 1923 a 1926

This doctoral dissertation deals with Heidegger's phenomenological concept of phenomenon, in Sein und Zeit and the Marburger Vorlesungen from 1923 to 1926.;Our study starts in Rein fund Zeta, paragraph 7. In this paragraph, Heidegger explicitly determines the concept of phenomenon, first formally, as what shows itself, but as it is not, Schein (¶ 7A), and then links this mode of showing with Being (¶ 7C). The Heidegger's affirmation according to which the phenomenon does not show itself (SuZ, 35) put forward by most commentators to support the thesis of the non-showing of the phenomenon, must be considered in the context settled by a reference to kantian transcendental philosophy (¶ 7A). The phenomenon does not show itself, that is, not in the same way that beings do; it shows itself at once and jointly with beings, but implicitly, and as it is not.;This interpretation finds support in two tasks assigned to phenomenology, as they deal with the problematic of the access to the thing itself. First, the ontological analytic of Dasein brings to the fore that Being shows itself together with the being designated for exam. Heidegger asserts it explicitly: the understanding of Being is already a positive phenomenon (SuZ, 5). Second, the destruction of the history of ontology reveals itself to be, initially, a task of appropriation, and then, a task of dismantling; its negative function, moreover, concerns only the present.;Our interpretation finds important additional support in the Marburg lectures that have prepared Sein und Zeit, as they reveal that the phenomenon is asserted from the start and persistently as Schein. During the winter semester 1923-1924, Heidegger speaks of a turnaround of the concept of phenomenon from what shows itself to what shows itself as it is not, under the effect of the facticity of language. In accordance with this discovery, the two following semesters (summer 1924 and winter 1924-1925) deal with the origin of falsity in language, falsity that reveals itself as Schein with particular eloquence in the Sophist lecture course. During the winter semester 1925-1926, Heidegger reiterates his concept of phenomenon as Schein by appropriating himself the kantian transcendentalism. The same concept is noticed during the summer semester of 1926, in the repetition of the discovery of Being from beings, which draw from Greek philosophy.;According to the most commonly accepted interpretation, the phenomenon is what does not show itself. This reading is accepted in France, in Germany as well as in the United States. In opposition to this interpretation, we defend that the phenomenon according to Digger is what shows itself, but what usually shows itself as it is not .;The understanding of the concept of phenomenon as Schein gives to phenomenology the sense Heidegger determined for it. The legitimation requirement proper to the method is reinforced, and the risk the philosopher sees to the enterprise of accessing the thing itself takes all its sense. Consequently, the entire project of Sein und Zeit takes on a new light.;Key words: philosophy, Heidegger, phenomenon, phenomenology, Sein und Zeit, Marburger Vorlesungen.