In this article, I assert the non-authenticity of the treatise Categories, attributed to Aristotle, by pointing to the theoretical inconsistencies of that treatise with Aristotle's doctrine of categories included in some of his authentic works : the Topics, the Sophistical Refutations, the Prior and Posterior Analytics, the Metaphysics. The article is divided into two parts ; in the first of which I concern myself with the author's doctrine of categories in his authentic treatises. I distinguish three levels of knowledge, linguistic, logical and ontological, in which the categories are opposed to, terms and forms (or parts) of speech, to predicables and to being, the most universal and trans-categorial predicate. I conclude that the categories are inter-categorial divisions of the predicate being and are intended to be predicated of all beings in order for these to be represented both in logical predication and in dialectical speech in conformity with the division of categories.