There is one fundamental argument in the Republic for the conclusion that justice is the greatest good. It begins in Book II; although adumbrated in Book IV, it is not completed until Book IX; and it draws essentially on material in Books VI and VII about Platonic forms, knowledge, and philosophical training. Justice consists in the rule of reason over spirit and appetite, but to understand the value of this state fully we must see how it is instantiated in the philosopher. Goodness consists in order, and by cognizing and loving forms (the most orderly objects there are) the philosopher possesses the highest goods. A fully just person is a creator and lover of orderly relationships among human beings. This condition exists to some degree in all just individuals, but it is most fully present in those who understand what justice is – philosophers.

This chapter offers a guide to reading Plato’s dialogues, including an overview of his corpus. We recommend first considering each dialogue as its own unified work, before considering how it relates to the others. In general, the dialogues explore ideas and arguments, rather than presenting parts of a comprehensive philosophical system that settles on final answers. The arc of a dialogue frequently depends on who the individual interlocutors are. We argue that the traditional division of the corpus (into Socratic, middle, late stages) is useful, regardless of whether it is a chronological division. Our overview of the corpus gives special attention to the Republic, since it interweaves so many of his key ideas, even if nearly all of them receive longer treatments in other dialogues. Although Plato recognized the limits inherent in written (as opposed to spoken) philosophy, he devoted his life to producing these works, which are clearly meant to help us seek the deepest truths. Little can be learned from reports of Plato’s oral teaching or the letters attributed to him. Understanding the dialogues on their own terms is what offers the greatest reward.

The chapter offers a reading of Socrates’ fourfold classification, at Philebus 23c-27c of “all the things now in the universe” into what is without limit (the apeiron), limit (peras), mixtures of these two (the meikton) and the cause of said mixtures (aitia). Contrary to the classification’s more typical treatment as a general window onto Plato’s late ontology and whatever may be its broader horizons, this classification is argued to be tailored to the project of the dialogue, directed to an analysis of the metaphysics of craft objects. In developing and explaining the classification, Socrates puts in place material for an analogy drawn from the craft of medicine to the effect that as medicine stands to health so stands some as yet unidentified craft to the good condition of soul that is the dialogue’s central focus, responsible for the happy human life. In thus articulating a framework for the historically influential idea of a craft of human living, Socrates provides a heuristic through which, in the remainder of the dialogue, the life’s character and elements may be systematically explored with a view to the dialogue’s overall contest between pleasure and intelligence.

The chapter aims to show that Plato’s engagement with mystery cults – the Eleusinian mysteries and Orphic cults in particular – can illuminate centrally important topics of Plato’s philosophy, including his conception of the philosophical life, its relation to the human good, the role of memory in the knowledge of the Forms, and the soul’s kinship to the divine. It explores why and how Plato presents philosophy as the true initiation which can fulfil the promise of the mystery cults to offer the best human life and afterlife. It analyses why and how Plato describes the knowledge of the Forms on the model of the direct encounter with the divine at the culmination of a mystery ritual. It further suggests that the ‘birth’ announced at the highest point of the Eleusinian mysteries can shed new light on the role of ‘giving birth’ at the culmination of the philosophical life in the Symposium. Finally, it shows how Pythagorean and Orphic focus on memory offered Plato a framework to develop his account of the relationship between the soul and the divine Forms, reincarnation, and the fate of our soul in the afterlife.

In the Meno, Socrates considers, and replies to, Meno’s paradox. According to the paradox, whether or not one knows something, one can’t inquire into it. The paradox has been understood in a variety of ways: some think it is invalid; others think it is valid but unsound; those who favor the second option disagree about what the false premise is. I argue that, as Socrates understands the paradox (but not, perhaps, as Meno does), it is valid but unsound: not knowing doesn’t preclude inquiry, since one can inquire on the basis of true beliefs that fall short of knowledge. Socrates develops this theme in the geometrical discussion with one of Meno’s slaves. Another part of his reply is the theory of recollection, which is often thought to posit innate knowledge. I argue, however, that, though the theory of recollection posits prenatal knowledge, it doesn’t posit innate knowledge. I also set the paradox in a broader context, exploring the Meno’s views on inquiry, definition, knowledge, and belief.

This chapter investigates Plato’s thoughts on poetic creativity by tracing a path from a traditional divine inspiration view to a new kind of inspiration, which transforms the poet into a philosopher. The path begins with divine inspiration in the Ion, then turns to the power of public poetry in the Gorgias. Next is the beginning of a new conception of poetic creativity in the Symposium. By considering poetry as a kind of communication between a lover and the beloved, Plato views poetry as a basis for a philosophical ascent to the Form of Beauty. In the Republic, Plato emphasizes further the power of poetry by classifying traditional poetry as a degraded kind of imitation. He highlights its power to corrupt the listener by strengthening irrational emotions. In the Phaedrus, Plato extends his notion of poetic creativity to linguistic communication in general, thereby developing further his notion of philosophical communication as a creative force generated by love. In the end, Plato pulls together both his denunciation of traditional poetry and his new conception of poetic creativity by offering a new type of public poetry in the Laws, consisting ultimately of his own body of laws.

This chapter addresses Plato’s conception of philosophy by examining how the Apology of Socrates represents Socrates as a model lover of wisdom. This Socrates loves expertise about how to live well, and he does so in three ways: (i) by examining others to test them for this expertise and to confirm that only the gods possess it, (ii) by pursuing the expertise, nonetheless, to improve his beliefs about how to live well, and (iii) by exhorting others to examine themselves and to pursue wisdom. The chapter pays special attention to Socrates’ conceptions of knowledge, living well, and teaching, and it suggests briefly how Plato tweaks or transforms this Socratic model in other dialogues.

The chapter asks if the first part of the Parmenides (including the “Third Man”) shows that Plato abandoned Platonic forms, and argues instead that Plato’s “Third Man” passage is not an indirect proof of anything: it simply shows the youthful Socrates not able to defend his views on forms. The exercise Parmenides then prescribes and demonstrates is the way forward Plato provided. It leads us to distinguish two kinds of predication, corresponding to two kinds of facts about forms. Better-organized thinking about forms lets us reject the notion that to perform their work in Plato’s theory, they must be perfect exemplars along the lines of “the Platonic ideal of the banana split.” This dispels the underlying problem which led to confusion over the “Third Man.” We can face down analogues of that argument for any form, from the Fox and Triangularity to Likeness and the Beautiful. This interpretation emerges from detailed construal of the text, taking account of both its literary and overtly philosophical aspects; the chapter brings together background for Plato’s agenda in his previous works, in the works of Anaxagoras and the historical Parmenides, and in Greek usage.

In Plato’s dialogues, Socrates calls things like justice, piety, and largeness “forms.” In several of these dialogues, he makes clear that forms are very different from familiar objects like tables and trees. Why, exactly, does he think that they differ and how are they supposed to do so? This chapter argues that in the Phaedo Socrates does not assume that they are different, but rather, over five stages of the dialogue, provides an account of how and why they do so. To fully understand the claims made in the first stage, one must look to the next stage, and so on until the final stage. Socrates' ultimate reason for distinguishing forms from ordinary objects does not depend on our intuitions about things like justice and largeness, nor on the distinction between universals and particulars. Ultimately, forms cannot be ordinary objects because the form of f-ness must cause every f-thing to be f, but no ordinary object could serve as such a cause. They cannot do so because they have multiple parts and are receptive of opposites; by contrast, the form of f-ness must be simple and unchanging, since it causes every f-thing to be f.