The two parts of this book require separate introductions. Although Part I (on method) comes first in order of presentation below, Part II (on metaphysics) was composed earlier and thus will be introduced first. Part II is a continuation of the inquiry into the metaphysics of Plato's late period that resulted in the publication of Plato's Late Ontology: A Riddle Resolved (PLO) in 1983.

PLO was concerned primarily with the once strange-sounding theses attributed to Plato in Aristotle's Physics and Metaphysics. Among them are the theses: (i) that numbers come from participation of the Great and the Small in Unity, (ii) that sensible things are constituted by Forms and the Great and Small, (iii) that Forms are composed of the Great and the Small and Unity, and (iv) that Forms are numbers.

Prior to PLO, there were two radically opposed positions on the significance of Aristotle's reports. One (represented by K. Gaiser and H. J. Krämer of Tübingen, among others) held that Aristotle was reporting a set of doctrines passed on orally by Plato but never committed to writing – the so-called unwritten teachings. The other position was championed by Harold Cherniss in The Riddle of the Early Academy, to the effect that Aristotle simply did not understand Plato's views and was reporting them erroneously. Opposed as they were in other respects, both camps maintained that the views attributed to Plato by Aristotle could not be found in Plato's dialogues.