The main objective of this Element is to reconstruct Aristotle's view on the nature of ontological priority in the Categories. Over the last three decades, investigations into ontological dependence and priority have become a major concern in contemporary metaphysics. Many see Aristotle as the originator of these discussions and, as a consequence, there is considerable interest in his own account of ontological dependence. In light of the renewed interest in Aristotelian metaphysics, it will be worthwhile - both historically and systematically - to return to Aristotle himself and to see how he himself conceived of ontological priority (what he calls 'priority in substance' [proteron kata ousian] or 'priority in nature' [proteron tēi phusei]), which is to be understood as a form of asymmetric ontological dependence.

The idea that some parts of reality are fundamental and others derivative was an important one in Aristotle's philosophical system, and is now again of great current interest in philosophy. Michail Peramatzis presents a new account of priority relations in Aristotle's metaphysics, and draws out their continuing philosophical significance.

Michail Peramatzis presents a new interpretation of Aristotle's view of the priority relations between fundamental and derivative parts of reality, following the recent revival of interest in Aristotelian discussions of what priority consists in and how it relates existents. He explores how in Aristotle's view, in contradistinction with (e.g.) Quinean metaphysical views, questions of existence are not considered central. Rather, the crucial questions are: what types of existent are fundamental and what their grounding relation to derivative existents consists in. It is extremely important, therefore, to return to Aristotle's own theses regarding priority and to study them not only with exegetical caution but also with an acutely critical philosophical eye. Aristotle deploys the notion of priority in numerous levels of his thought. In his ontology he operates with the notion of primary substance. His Categories, for instance, confer this honorific title upon particular objects such as Socrates or Bucephalus, while in the Metaphysics it is essences or substantial forms, such as being human, which are privileged with priority over certain types of matter or hylomorphic compounds (either particular compound objects such as Socrates or universal compound types such as the species human). Peramatzis' chief aim is to understand priority claims of this sort in Aristotle's metaphysical system by setting out the different concepts of priority and seeing whether and, if so, how Aristotle's preferred prior and posterior items fit with these concepts.

Aristotle's views on the fundamental nature of reality are usually taken to be inconsistent. Two sources for these views are Categories and the central books of Metaphysics. This text argues that he is engaged in different projects in these books.

This volume is about ontological categories. The categories of an ontology are designed to classify all existents. They are crucial and characterize an ontology.

Cleary discusses the origin, development, and use of the many senses of priority as a central thesis in Aristotle's metaphysics. Cleary contends that one of the most revealing problems for the ambiguity of Aristotle's relationship to Platonism is that of the ontological status of mathematical objects. In support of his claim, Cleary analyzes a curious passage from Aristotle's Topics, where he appears to accept a schema of priorities that makes mathematical entities more substantial than sensible things. How does Aristotle try to reconcile the ordering of things dictated by sciences like mathematics and dialectic with the ordering of sense experience upon which his own physics and metaphysics are based? To find the answer, Cleary reviews three different outlines of the many senses of priority given by Aristotle himself and found in Categories 12-13, Metaphysics Delta 11, and Metaphysics Theta 8. Cleary suggests there is an implicit hierarchy for Aristotle that leads him to posit the Prime Mover at its apex as complete actuality and, therefore, as the focus for the concept of priority. Having reviewed Aristotle's treatment of the many uses of priority, Cleary demonstrates how the concept is used in some typical arguments by Aristotle for his mature metaphysical positions.

A new interpretation of Aristotle's metaphysics, a subject of considerable interest to all classical philosophers.