What do you think? — 180 Proof
I think Murdoch speaks for herself and not for philosophy or poetry. In the video she is quoted as saying
... the aim of philosophy is to clarify and the aim of literature is to mystify.
(3:54)
While I think it is certainly true that Plato attempts to clarify, I think it also true that part of what he attempts to clarify is the ontological and epistemological mystery. Not in order to demystify but to allow the mystery to stand.
Mystikos in the Greek sense of secret, not revealed or disclosed or known. Plato plays on the double sense of hidden/revealed and uninitiated/ initiated. In the Republic the philosophers are philosophers because they have undergone a transcendent and transformative experience. But this imagined philosopher is at odds with Socrates, who knows that he does not know, as well as with the characterization of the philosopher in the Symposium as one who desires to be wise but is not. The Socratic philosopher is one who pursues but does not possess wisdom beyond the human wisdom of knowing he or she is ignorant.
Looked at from the side of poetry or literature, I think it questionable that it is to be read:
... only or principally as 'literature' – for their literary qualities. — 180 Proof
It should be kept in mind that at the Plato lived the poets were the primary source of public education. They serves not simply to entertain but to educate. A fundamental question for Plato is, who will be the educators? In terms of the cave, who are the puppet-masters? Plato took seriously what the poets said about men and gods.
Murdoch says that philosophy should develop a moral or philosophical psychology that provides the terms in which to understand and characterize the substantial self to which she gives center stage, displacing the existentialist/analytic (which she sometimes calls “existentialist-behavioristic”) freely choosing will. (SEP Iris Murdoch)
Such philosophical psychology can be found both in Plato and the Greek poets.
As I understand it, Plato's concern was not simply to draw the battle lines in the quarrel between the philosopher and the poet as to present a philosophical poiesis. To this end he made full use of the imagination and its images, including the images of the cave, the divided line, and the philosopher.
Along the same lines, he does not simply take sides in the quarrel between philosophy and sophistry. He makes use of sophistic arguments when we thinks it appropriate in order to persuade. Not in order to make the weaker argument stronger, as the sophist does, but to arrive at the argument that is on its own merits stronger. It is here, with regard to persuasion, that his suspicion of both poetry and sophistry lies.
Both poetry and sophistry are philosophy's competitors in the task of persuasion and education. In addition, he competes against the politicians and theologians, creating his own city, albeit only in speech. A city in which the philosopher rules, in which the sophist (Thrasymachus) is tamed and made an ally, in which the philosopher is the myth maker, and the gods are replaced by the Good.
As to the education of the philosopher - escape from the cave means to free oneself from all puppet-masters, all makers of images, be they poets, sophists, politicians, theologians, and even philosophers.