(en) The objective of this thesis is to provide an ontological study of the concept of speech in Martin Heidegger philosophy by proposing a dialogic reading which is focus on an exemplary concept of nothingness. This conception takes place in a continual tension between destruction and appropriation, where lies the logic of Heidegger in his "repetition" of poets and philosophers of German idealism. Dialogical tension, underpinned by a single unifying principle, the nothingness at the heart of a logos that becoming poetic, but still meaningful for human finitude. This study avoids a double trap where many misinterpretations of the logos of Heidegger are linked : to ask that depends on the idealism of hegel and platon is Heideggerian metaphysics, thus open to the mythological poetry and therefore contaminates the scientific and historic phenomenology, which comes of Aristotelian and Kant. The author shows instead that we can not restrict the analysis nor as an abstract concept of the mythology since it is primarily through his dialogue with firsts philosophers Heraclitus and Parmenides that we can find the phenomenological source of Heidegger's poetics logos, so much so that only that which is experienced existentially in the heart of the becoming understood as the place of the original unity of each phenomenon, presided over the emergence of any human word which can mean ontologically. The thesis therefore attempts at the same time to present a phenomenological reading of poetry by returning to the basic unit of the ontology, this from the Hegelian concept of unification thematized by O. Depré and so present the phenomenological unity as heart of mythic, idealistic, scientific and historical visions of philosophy: thinking of the One is giving through a plurality of paths distinct each others.