"Ciò la cui nozione è una definizione è un'unità" (Met. Z 12, 1037 b 11-12):in che cosa la definizione dell'essenza differisce dalla semplice definizione di un concetto?

Along Metaphysics Zeta Aristotle repeatedly underlines the correspondence between the parts of the horismos (understood as the definition of the essence of the ousia) and the parts of ousia understood as concrete being: Horismos and ousia are both to be considered as wholes consisting of parts united by means of an internal bond. In order to understand the peculiarity of the horismos it is useful to compare it to the Socratic search of the ti esti, on the one side, and to the Sophistic technic of definition on the other side. This task is developed in the first part of the essay (pp. 49-59). The second part (pp. 59-74) pinpoints how the complexity of the Aristotelian search of the definition of the ousia rests on the dialectic method of the inquiry, whose results are always partial and seldom definitive. This characteristic has a great heuristic value in so far as it allows to discern a continuity in the thread of the argumentation between Zeta and both the previous (Gamma, Epsilon) and the following books (Eta, Theta). A shortened version of this essay was presented to the Annual Conference of SISFA (Società Italiana di Storia della Filosofia Antica) Rome, La Sapienza, 30 October 2013.