The Dream of Enlightenment by Anthony Gottlieb review

Quite plainly, we don't know. It seems irrelevant, however, as the line of inquiry was about whether the article-author mistakenly attributed the Allegory of the Cave to Socrates when the 'correct' attribution is to Plato (that is, the established/agreed-upon/canonical attribution), not whether or not the Allegory is a wholly original, purely inspired, spontaneously birthed thought from Plato.

In regards to the ideas truly being Socrates' or those of a precedent, I'm aware of nothing that indicates that being the case (other than the standard A influences B influences C, etc, nature of philosophy). I'm no expert, but it seemed clear to me in reading Plato's work after the death of Socrates (e.g., Republic) that he is radically departing from the views of his teacher. If the counterpoint is that Plato received all of this wisdom from Socrates, then attributed the introductory bits to his teacher and kept the juiciest for himself, we know that's not the case: many other contemporaries wrote about the views of Socrates and some even recorded Socratic dialogues.

In Republic, Plato advocates things like an elite intellectual class that actively deceives the hoi polloi and prevents them from accessing philosophy, yet Socrates was put to death for his repeated attempts at engaging all Athenians who would listen in philosophical debates. Socrates warned against the youth of Athens losing their ability to think critically, while Plato advocates a utopian system predicated on the vast majority of its citizens not questioning things at all. In fact, it's frequently suggested that Plato's dramatic departure from the Socratic notion of "I know nothing" and the near-totalitarian features of his Republic are direct results of the Athenians turning on and executing Socrates. The entire idea of a Philosopher King and an enlightened ruling class micromanaging the lives of the producer/worker and guardian/soldier classes seems like a plan to ensure that no great thinker ever suffers the same fate as Socrates. With the rebellious and reactionary nature of the Republic established, it seems clear he didn't get the ideas contained within from Socrates. This seems especially true because Plato does not discuss them until ~380 BC, almost two decades after the death of Socrates. If he inherited or stole the ideas, why wait so long to talk about it? And why didn't anyone else know about it (Plato was one of several students who followed Socrates)?

I've glanced, very lightly, over the Wikipedia page for the Eleusinian Mysteries, and there's nothing specific leaping out at me as inspiration for the Allegory of the Cave (other than the idea of a layered underworld, but that's not unique to the Mysteries or particularly reflective of the Cave). I'm unfamiliar with these ideas; can you expound upon the connection, or is the argument just that because the Mysteries were ancient and once orally disseminated, there's a chance that the Allegory was too and merely reported by Plato as original?

Just to give you a taste of what to expect though: imagine a lot of very smart people considering the sorts of issues Feynman is raising, but devoting whole books to them, trying to cover these issues from every conceivable angle and taking in to account all of the other points of view on these issues (not just those of Feynman himself or some astrologers or psychics, as Feynman did). Then there are the books in response to those books, trying to be just as thorough in answering the questions the the first author wrote about, and seeing if there's something they missed or any other constructive way to think about them, and so on.

In short, there's an entire academic field that studies these questions and many other related ones, that isn't going to be covered by a little essay by any single scientist -- no matter how brilliant he was. He didn't have the final word, and not even much of a word in the first place, considering his lack of study of and engagement with the field.

Feynmann's own words in the essay on "Cargo Cult Science" are salient here:

"It’s a kind of scientific integrity, a principle of scientific thought that corresponds to a kind of utter honesty--a kind of leaning over backwards. For example, if you’re doing an experiment, you should report everything that you think might make it invalid--not only what you think is right about it"

It's telling that Feynmann does not apply this principle of integrity to the views he expresses in his own essay. He does not, even for a moment, write about what could possibly be wrong with his point of view. But such questioning is quite common in the philosophy of science. They don't stop with dogmas and ideals regarding what science ought to be, as Feynman does. They go further and question them, and much else besides.

By "do better" I mean in an equivalent few pages to advise a new graduate about how to discover things that are true, as a focus sometimes at odds with advancing their career, because that's what Feynman's graduation speech was about.