In almost every handbook and in almost every history of philosophy you will find the thesis that Aristotle in Metaphysics Z has developed a theory about substance – an imperfect one unfortunately. From the Middle Ages until now this has been the most widely accepted claim about this book. Because the basis for this claim is not so easy to find in the text, there is a dispute about the question what a substance really is and ”which things“ are substances. (...) But the theory itself remains. If you engage to clear the field of problems in which this book has its roots, you will see apories developed by Plato in his dialogue Sophistes, mainly the apory in the middle of the dialogue. Here the guest from Elea is led to the question ”What in the world do we have to understand by the term ’to be’?“ ”...For you evidently understood the matter long ago; we, on the contrary, before thought we understood, but now are in trouble about it.“ Aristotle repeats this question, the question about being, on a new level and with new conceptual tools. In the Topics he develops what I call the ”topical approach.“ The use of it is suppported by a new type of concepts, the quotations (e. g. to ti estin: ”Say what you mean, if you ask 'What is this?'“ The standard translation ”essence“ makes impossible to see the genuine meaning of the term.) In Metaphysics Z he puts in concrete terms what in Metaphysics Λ was just a sketch of his speculation about ”to be.“ Seeing this background, it becomes clear that Metaphysics Z never contains the expected theory, which many allege that Aristotle is defending. This is no more than the remains of the pastristic and medieval interpretation. The German translation with commentary which I submit with this book, and an extensive introduction to these questions, should contribute to the destruction of this part of metaphysics. (shrink)