This study addresses major problems in interpreting Aristotle, such as whether the reader should reconcile the apparent inconsistencies of the corpus by assuming an underlying unity of doctrine (unitarianism), or by positing a sequence of developing ideas (developmentalism).

The two systems hypothesis; S1:Atomic substantialism; S2:Hylomorphic substantialism; The incommensurability of the systems; The hylomorphic turn; The growth of S2:The four causes; The growth of S2:Potentiality and actuality; The paradoxes of substance: matter; The paradoxes of substance: form; S1 without S2: What Aristotle should have said; The two systems theory as an interpretation of Aristotle

`the book has considerable merit and deserves to be read. The thesis ... is an interesting one, and his arguments for it are learned and well articulated' Review of Metaphysics `Any investigation of Aristotle's philosophical development must now take Daniel Graham's book as its starting-point, and every serious student of Aristotle should read it.' Times Literary Supplement `What is new - and what makes Aristotle's Two Systems so exciting - is the way in which Graham has constructed a comprehensive physiognomy of the two metaphysical systems, and the extremely powerful set of exegetical arguments upon which he bases his account of Aristotle's handling of them.' Times Literary Supplement `This persuasive view of Aristotle has not previously been developed in anything like such a careful and wide-ranging way. It is written with the clarity which one has come to expect in the best Aristotelian scholarship, and is an important contribution to ancient philosophy.' Times Higher Education Supplement