As the second section of the preceding chapter indicated, fundamental ontology sets itself the task of restricting the sphere of validity of Greek ontology in showing that the ontology of ousia is valid only, and to a limited degree given the analysis of Zuhandenheit, for the beings that we are not, for innerworldly beings. One might say that if both the concepts of existence and essence derive from an interpretation of the finished product, then in distinguishing human Existenz from the sphere of the categorial, phenomenology must show that Dasein never is a finished product. Although we may describe someone who has attained a certain degree of excellence in this way, for Heidegger Dasein is always and already ahead of itself because its Existenz is what he terms a "being-possible (Möglichsein)' or a "potentiality-for-being (Seinkönnen)' [SZ 143].