Abstract
Our goal is to investigate the extent of the appropriation, by hermeneutic phenomenology, of the concept of transcendental at work in descriptive psychology, where it plays the role of a universal principle of the constitutive genesis of intentionality. We aim to clarify how the very mode of operation of Husserlian phenomenology is crucial to the elaboration of fundamental ontology. Our hypothesis is that intentionality leads Heidegger to the discovery of time as a transcendental principle, of being as an a priori, and of comprehensibility that enables the signification of entities in general as a previous structure of the a priori.