The general topic of my philosophical dissertation is phenomenological ontology of breathing. I do not investigate the phenomenon of breathing as a natural scientific problem, but as a philosophical question. Within our tradition, breathing has been normally understood as a mechanistic-materialistic physiological life-sustaining process of gas exchange and cellular respiration which does not really seem to have any essential connection to human being’s spiritual, mental or philosophical capacities. On the contrary to this natural scientific view, I argue that breathing can (...) be understood as a philosophical question that has phenomenological, experiential, ontological, spiritual, bodily, mental, poetic, elemental, ethical, voluntary and mystical dimensions. My investigation conceptualizes breathing in the first place as a question of phenomenological ontology. Maurice Merleau-Ponty’s phenomenologico-ontological method of interrogation of the lived body’s experiential openness to the world and Being provides the most fundamental point of departure in this dissertation. Merleau-Ponty emphasized in his investigations the lived body’s perceptual openness to the world and Being. He argued famously for the primacy of perception. His thesis of the primacy of perception means that perception as the perceptual openness to the world and Being is the foundation which is always presupposed by all the other levels of our existence and being-in-the-world. In this dissertation, I challenge this idea of the primacy of perception with Merleau-Ponty’s own remarks about breathing. I argue that in his own remarks about breathing, he implicitly points toward a level which is even more fundamental than the primacy of perception. In this dissertation, this level of our being-in-the-world I call the primacy of breathing. Breathing as the lived body’s respiratory openness to the world and Being is now understood as the foundation which is always presupposed by all the other dimensions of our being-in-the-world. These dimensions are, for example, our theoretical, practical, social and perceptual ways of relating with the world. If the idea of the primacy of breathing is taken seriously, it means that all the questions of philosophy could be rethought, reexamined and re-experienced within the fundamental atmosphere of respiratory openness to the world and Being. In this dissertation, I initially try to rethink philosophy as a new philosophy of breathing. This new philosophy of breathing would be phenomenological ontology of breathing. The bases of this new phenomenological ontology of breathing are Merleau-Ponty’s remarks about breathing. My task is to explicate and interpret them with the help of Merleau- Ponty’s own phenomenological ontology. In my task of beginning philosophy anew as philosophy of breathing or as respiratory philosophy, I will also use the ideas of Martin Heidegger, Gaston Bachelard, Paul Claudel, Luce Irigaray, Edmund Husserl and David Kleinberg-Levin. My dissertation is divided into two main sections. In Section One, I construct within the framework of phenomenological ontology a new notion of breathing as the primacy of breathing. In Section Two, I develop a phenomenological method that I call the method of ontologico-respiratory reduction. This method will lead us back to the primacy of breathing. (shrink)