Each of the two major approaches to Aristotle--the unitarian, which understands his work as forming a single, unified system, and the developmentalist, which seeks a sequence of developing ideas--has inherent limitations. This book proposes a synthetic view of Aristotle that sees development as a change between systematic theories. Setting theories of the so-called logical works beside theories of the physical and metaphysical treatises, Graham shows that Aristotle's doctrines fall into two distinct systems of philosophies that are genetically related.