How much is known about Plato's "unwritten doctrines"?

Question

It is often claimed in the historical literature that Plato's teachings were divided into the written documents (his famous books, like The Republic, The Laws etc) and oral teachings (what Aristotle called the "unwritten doctrines") . Some scholars even claim that the best and most important part of his philosophy was precisely the oral one, delivered in the Academy, while the dialogues were merely intended for philosophical dissemination. This hypothesis is supported, among others, by the works of the Italian historian Giovanni Reale.

This view, however, has been disputed by other scholars. In The Cambridge companion to Plato, for example, the author writes:

There is no evidence to suggest that there was a large body of oral doctrine constituting a complete system that would underlie, explain, or undermine the dialogues. [...] There is no evidence to suggest that Plato or anyone else took his oral teaching any more seriously than he took the dialogues.

Has there been recent studies on this subject? Is there any compelling recent evidence for – or against – the hypothesis that the "unwritten doctrines" were the main part of the Platonic philosophy?

Answer 1

I should preface this by saying that I am not a classicist, and will gladly defer to anybody who is more up on the literature than I am.

That being said:

There are the occasional folks who claim to have uncovered signs of Plato's hidden doctrines within the Platonic corpus. For example, Jay Kennedy believes that Plato was a secret Pythagorean, and that there are musical clues encoded in his writings. As you might expect, this is far from a mainstream view.

The mainstream view, as you indicate above, is that there is no historical evidence of any unwritten doctrines outside of a small number of references in Aristotle (and Aristotle's epigones.) Occasionally, you will find a historian attempting to tease something out of the references, such as this article, but the passages are so brief as to permit only highly speculative readings.

In short, we don't know, and have no way of knowing, what Plato didn't write.

If your interest is not so much in the content of the unwritten doctrines, but in the fact that they were oral and not written, there is a body of literature on Plato and the transition from Orality to Literacy. Eric Havelock's Preface to Plato is the primary work on the subject, but it is almost half a century old. A more recent (but briefer) trip through the material can be found here.

Answer 2

Plutarch tells us that when Alexander heard that Aristotle had published some of his philosophy, he wrote to Aristotle to remonstrate him for doing so.

“For when he was in Asia, and heard Aristotle had published some treatises of that kind, he wrote to him, using very plain language to him in behalf of philosophy, the following letter. ‘Alexander to Aristotle, greeting. You have not done well to publish your books or oral doctrine; for what is there not that we excel others in, if those things which we have been particularly instructed in be laid open to all? For my part, I assure, I had rather excel others in the knowledge of what is excellent, than in the extent of my power and dominion. Farewell.’