In this volume R. resumes the project of his earlier Real Ethics: Reconsidering the Foundations of Morality (2002), in which he argued for theistic Platonic realism as the only philosophically viable alternative to moral nihilism and relativism. While Real Ethics engaged with debates in contemporary metaethics, the present volume returns to Plato's own struggles with these problems, from his early work on the puzzles of Socratic definition to the grand metaphysical speculations of Phaedo and Republic and the sophisticated and self-critical arguments of the Parmenides, Sophist and Timaeus. In the course of this development, R. contends, Plato arrived at conclusions of enduring value about the metaphysical and psychological presuppositions of ethics: that objective moral standards and obligations, if they are to exist and moral practice is not to collapse into the mere expression of preferences or conventions, must be grounded in transcendent, unchanging Forms, especially the Form of Good; that an immortal human soul must have an innate capacity to grasp and be motivated by these entities; and that the Divine Mind must exist as an efficient cause to explain how these Forms become instantiated in the material world of change (pp. 242–52). R. explains his purposes in his introduction: ‘I wish to show in much more detail [than in Real Ethics] how Plato arrived at his realism (together with his complementary claims about philosophical psychology) and how he defended it … My aim is less to argue for the existence of Platonic Forms than to urge that without such Forms … moral nihilism – in Plato's view (and my own) – cannot be defeated philosophically’ (p. 5).

The text's main body consists of a rough chronological review of the dialogues, as R. traces the key arguments and claims that represent important movements in the development of Plato's thought. In early dialogues like Laches, Gorgias, Hippias Minor and Protagoras, we see Socrates examining the prominent Greeks, revealing their ignorance on moral matters (pp. 30–1). Gradually, however, Plato begins to understand that deeper investigations are required to make substantive philosophical progress. In the Meno, for instance, ‘the groundwork is being laid for the straightforward conclusion that Socratic questioning – a dangerous activity not least because itself open to abuse … is only the first stage of a desirable philosophical journey’ (p. 49). Through the Meno, Cratylus, Symposium and Phaedo, as R. explains, Plato begins to develop and explore the epistemological, metaphysical and psychological conditions necessary to make good on Socrates' optimistic but ultimately ungrounded faith in an objective ethical truth that can be the proper object of philosophical inquiry.

The heart of Plato's argument for moral realism, according to R., occurs in the Republic, a dialogue to which R. devotes his longest central chapter. He explains:

Plato's thesis – which R. endorses – is that ‘all “third ways” between Socrates and Thrasymachus are logically confused or fudges. Any non-Socratic proposal will ultimately be found on the Thrasymachean side of the line’ (p. 114). The Republic seeks to make good on this thesis, developing ambitious new proposals in psychology (the tripartite soul, which explains ‘the conflict between our various sets of desires, for the good and for lesser or apparent goods’) and metaphysics (in particular, subordinating all Forms to the Form of the Good) (p. 164).

In subsequent dialogues, Plato continues to work through unresolved problems created by the Republic's bold psychological, epistemological and metaphysical ideas. The Parmenides and Sophist explore and attempt to resolve problems about the scope and order of the Forms and their relation to material reality (pp. 174–6; 200–5). The Phaedrus builds on the Republic's psychology, introducing an intractable psychological motivation toward evil in the soul (p. 189). Finally, in the Philebus, Timaeus and Laws, Plato explores the metaphysical role of God as ‘the organizer or “mixer” whose effects are always positive’ (p. 212). In these latter texts, R. finds indications that Plato considered identifying the Form of the Good with the Demiurge, making the combined Form of the Good/Divine Mind not only the formal and final cause, but also the efficient cause of the universe (p. 241). Though the evidence that Plato himself made this further move is not definitive, R. suggests that it would solve many of the remaining unanswered problems in Plato's theory (p. 252).

In the final chapter, R. steps back to consider the ongoing relevance of Plato's ethics. He briefly addresses alternative metaethical approaches (naturalism, Aristotle's ethics, Kantianism, etc.), arguing that each either collapses into nihilism or relies on hidden metaphysical assumptions that imply Platonism. Summarising a key argument, he explains:

As R. admits, further work must be done to supplement and develop Plato's moral realism and ‘to tie together some of the loose ends he left hanging’ (p. 265). In particular, R. recommends identifying the Form of Good with God, thus personalising the fundamental principle of reality, while making moral Forms attributes of the Divine Mind and substance Forms its ideas (pp. 266–9). Nevertheless, R. is convinced that Plato's general chain of reasoning remains inescapable for anyone seriously committed to understanding the possibility of objective moral truth (pp. 268–9).

R.'s reading of Plato's philosophical development is plausible and compelling, though specialists expecting close textual readings and engagement with the secondary literature will be disappointed. In this way, R.'s book belongs to an earlier tradition of Plato scholarship, as it seeks to survey the broad sweep of Plato's thought, while avoiding getting caught up in the details (p. 13). R.'s response to the unitarian–developmentalist debate in Plato scholarship is also attractive. On his interpretation, Plato's views show considerable development over time, reflecting Plato's admirable ability to engage in self-criticism and work to address problems created by his own earlier proposals. At the same time, Plato remains motivated throughout by the core set of ethical problems and questions inherited from Socrates, which provides continuity to his work. R.'s methods necessarily gloss over many nuances, leaving the impression that Plato was more dogmatic than, in my view, many of the texts merit. The overall interpretation, however, provides an instructive overview of Plato's career.

On the other hand, R.'s conviction that Plato was right, and that his theories form at least the core of the only respectable alternative to moral nihilism, is more dubious. Certainly, the metaphysical status of morality remains a vexing problem, but to claim that no approach other than Platonic non-naturalism can succeed both neglects strong work done by proponents of alternative approaches and glosses over significant problems faced by Platonic theories themselves – problems which led many philosophers, including most subsequent ancient Greek ethicists, to reject Plato's approach.