Aristotle was the founder not only logics but also of ontology which he describes in Metaphysics and Categories as a theory of general properties of all entities and categorical aspects they should be analyzed. Meanwhile it is commonly accepted that we inherited from him not one but two different logics: early dialectical logoi of Topics and later formal syllogistic of Prior Analytics. The last considers logics the same way as the modern symbolic logic do. According to J. Bocheński the symbolic logic is “a theory of general objects” (by apt turn in phrase, a "physics of the object in general”) hence logics, as it is interpreted now, has the same subject as ontology. But does Aristotle himself counts that ontology (as it is accepted to speak now) is just a kind of “prolegomenon” to logic? In the paper some aspects of this issue are studied at length.