Αἴτιον ἐνυπάρχον: “That which is also at hand therein” in such a way of being, in the function of the αἴτιον τοῦ εἶναι. The ψυχή is such a being-character. To say that the soul is οὐσία is to say that it is a being-character that is at hand in a being in the aforementioned sense. The soul is also at hand therein in such a way that it also constitutes the specific being of that which we call living. It is responsible for, or constitutes, the specific being of a living thing, namely, of a way of being in the sense of being-in-a-world. The two basic aspects are κρίνειν and κινεῖν. A living thing is not simply at hand (as accessible to everyone), but is there in its being-at-hand in an explicit mode. It can see, do, move itself. The two aspects of this οὐσία are κρίνειν, “separating” from something other, orienting itself in a world; and κινεῖν, “moving itself therein,” being-involved-therein, going-around-and-knowing-its-way-around-therein.” Thus, when one speaks of Greek philosophy, one must be careful with the famous “substantiality” of the soul. Οὐσία means a mode of being, and if the soul is called οὐσία, it refers to a distinctive mode of being, namely the being of the living. (Heidegger, GA18:30-31)