Capra, Andrea. 2015. Plato's Four Muses: The Phaedrus and the Poetics of Philosophy. Hellenic Studies Series 67. Washington, DC: Center for Hellenic Studies. http://nrs.harvard.edu/urn-3:hul.ebook:CHS_CapraA.Platos_Four_Muses.2014.
Introduction. Plato’s Self-Disclosing Strategies
What is a Platonic Dialogue? Poetry and Knowledge
- Plato’s Academy was sacred to Apollo and the Muses, the latter having their own altar (e.g. Pausanias 1.30.2). The tradition was further promoted by Plato’s immediate successors. 
- Not only does Aristotle include Plato’s dialogues in the Poetics, where he defines them in terms of mimêsis and poetry (1447b), but many others, including Platonic philosophers, regarded Plato as a poet, even a new Homer (e.g. Proclus on Plato’s Republic 1.196.9–13 Kroll). 
- Time and again, Plato’s dialogues refer to philosophy as the highest form of mousikê (e.g. in the Phaedo 60e–61a). Needless to say, the dialogues abound in myths and even invocations to the Muses (e.g. in the Phaedrus 237a, and in the Republic 545d). 
- Plato’s dialogues were sometimes recited during symposia along with excerpts from comedy (cf. e.g. Plutarch Table Talks 711b–c). 
- The anecdotal tradition reports that Plato, a former tragic poet (e.g. Dicaearchus fr. 40 Wehrli), was strongly influenced by the mimes of Sophron as well as by the comedies of Epicharmus and Aristophanes. 
- Plato himself, or at least the characters of his dialogues, seem to allude to his output as if it were a kind of song or drama.
Ευ. δεξιότητος καὶ νουθεσίας, ὅτι βελτίους γε ποιοῦμεν
τοὺς ἀνθρώπους ἐν ταῖς πόλεσιν
Aeschylus: … Come, tell me: why should we admire a noble poet?
Euripides: For his ready wit and his good counsels
and because we make men better in our cities.
Needless to say, this passage has its own function within the comedy, and yet, in all probability, it represented widely accepted ideas.  The Athenians voted to allow the Frogs to be produced again by anyone who wished to do so, and thus it became the first comic classic in history.  In the same comedy, moreover, we hear that the degradation of Euripides’ poetry is tantamount to its losing the status of mousikê, which only confirms the relevance of the distinction I make above between “musical” and “non-musical” arts. 
Interestingly, Lycurgus credits the poets with quintessentially philosophical procedures such as “argument” (λόγος) and “demonstration” (ἀπόδειξις).
Towards a Self-Definition of Platonic Dialogue
Halliwell emphasizes the relative novelty of such an approach, especially as regards scholarship in English, and he shows how effective it can be by very successfully highlighting the subtle (and no doubt self-conscious) ambiguity of Plato’s attitude towards poetry in the Republic. In fact, Halliwell’s “explicit moments of self-consciousness” had long been studied by one of the most important Platonists of the 20th century, namely Konrad Gaiser.
Prologue to the Phaedrus
ἡδυεπής, τέττιξιν ἰσογράφος, οἵ θ’ Ἑκαδήμου
δένδρει ἐφεζόμενοι ὄπα λειριόεσσαν ἱεῖσιν.
And a plate-fish was leading them all, though it was a speaking one,
and sweet-voiced at that! In his writings, he matches the cicadas,
pouring out their lily song from the tree of Academus.