Aristotle clearly realized that his analysis was seriously complete. When he returned to the task in the lectures later put together as Metaphysics his overriding concern was with being as being.
And indeed the question which was raised of old and is raised now and always, and is always the subject of doubt, viz. What being is, is just the question, what is substance?. . . And so we also must consider chiefly and primarily and almost exclusively what that is which is in this sense. (Metaphysics, 1028b 1-6, italics in McKeon)
His metaphysical account is a theory of being as composite of matter, form, and potency that seeks to make change intelligible. This doctrine applies primarily to substantial beings. The net result is that the things that count as subjects of scientific investigation are things belonging to types that admit of definition, at least in principle. Scientific investigation and demonstration is primarily concerned with things categorized as substantial units, which are characterized by their quantity, quality, relation, action, passion, plus further categories, and which can remain substantial units while undergoing accidental changes.
The Aristotelian categorial system, though rooted in basic features of the Greek language, was intended as a means of accounting for reality as it exists objectively. Aristotle treated categories both as 'kinds of predicates' ( ) and 'kinds of being' ( ). The boundary is fuzzy. Yet, one clear separation constitutes a basic requirement of Aristotelianism. Some properties are essential for natural kind objects to be natural kinds, regardless of the language in which these properties are expressed. In making individual objects the units to be explained and in striving to make basic explanations independent of the features of any particular language Aristotle initiated the language of physics.
The subsequent evolution of the categorial system involved an increasing detachment from its basis in normal language usage. This heightened the appearance of objectivity, of categories as kinds of beings. Aristotelian writings were transmitted to the West through the medium of works written in Arabic, a non Indo-European language. The earliest Arabic philosophers, Al-Kindi (c. 790-873) and Al-Farabi (c. 870-950) assimilated Aristotelian philosophy through late neo-Platonic commentators. Both insisted that Plato and Aristotle really held the same metaphysics and differed only on terminology. This syncretism discounted the type of language analysis that both Plato and Aristotle used in establishing their positions. Aristotelian philosophy achieved a certain degree of distinctiveness as philosophy and autonomy from the Koran only in the writings of Averroës (1126-1198). He knew the corpus of Aristotle's writings. To combat Al-Ghazzali's (1058-1111) neo-fundamentalist attack on philosophy Averroës distinguished three classes of men: the religious man, who recites the Koran; the lawyer, who interprets the Koran; and the philosopher, who deals with absolute truth and interprets the Koran as allegorical. Though Al-Ghazzali's position became dominant in the Islamic tradition, Averroës had the major influence in the West.
When Aristotelianism was introduced in the West in the mid-thirteenth century the Aristotelian categories were accepted as an objective classification, and their ordering was interpreted as expressing a conceptual necessity. A quality, such as red, presupposes an extended substance. Extension presupposes something extended, a substance. Substance is not predicated of anything. Thus in the order of being, as opposed to the