Abstract
Heidegger’ s Prolegomena zur Geschichte des Zeitbegriff offers what could be called a phenomenology of Phenomenology itself, that is: an investigation of its history. The husserlian discovery of the “categorial intuition” appears as the second moment of this history, after Brentano’s “intentionality” and before Heidegger’s own discovery of the “original sense of the a priori”, which constitutes the third moment. Our paper seeks to understand this sequence as a way to answer the leading question of how it may be possible that “to be a intentional object can have any relationship with the being itself”. Or, to put it in another formulation: how is intentionality itself ontologically possible?