This research paper analyses how, by developing the metaphysics of human life of the Spanish philosopher Ortega y Gasset, his disciple Julián Marías has discovered the subject of the person as a philosophical matter and how, especially in his work Antropología metafísica (1970), he has developed the appropriate philosophical concepts to understand it: empirical structure, installation, vector, corporality, temporality, sexual condition, etc. In his work Persona, the philosopher has defined it as “radical innovation of reality”, which has deep metaphysical implications, coming from the philosophy of vital reason of Ortega y Gasset, who, in contrast to idealism and realism, considers that life is the radical reality, in which all other realities find their root. This means that the person, a “corporeal someone”, is fully a who, he who lives, and must be thought of with personal categories that give reason for his character irreducible to any other reality.