Roochnik is surely more familiar with the works of Plato than I am, but his thesis that "Plato wouldn't conceive of ethical philosophy as techne" flies in the face of much of what Plato and his school explicitly says. To Plato, things like goodness and virtue are real, just as much or moreso than the nose on your face. Knowing about them is then every bit as much of a technical problem as is knowing the distance from the earth to the sun. Many of Plato's works explicitly draw parallels between proof construction in geometry and proof-construction in ethical philosophy, and for that matter, the neoplatonist Plotinus makes much use of the concept of a "sage," namely someone who actually has figured out moral truths once and for all, perfectly (although, I don't know off the top of my head whether Plato also believed in sages, nor do I know if there's a well-accepted opinion on whether Plotinus thought that a sage ever had or would exist.)
Certainly, bright modern-day scholars attributing beliefs to older thinkers that the thinkers themselves outright deny is a thing that happens, and is a healthy part of respectable humanities research. E.g., people who talk about Nietzsche being nihilist or anti-semitic, who left us so many diatribes against nihilists and anti-semites. The humanities wouldn't be interesting if people took their source materials at their word! But its worth keeping in mind how counter-intuitive Roochnik's claims are. (And to his credit, he mentions as much several times.)
I also wonder whether his central piece of evidence, namely that Plato wrote dialogues rather than treatises, isn't projecting relatively-modern writing sensibilities onto an ancient Greek. Plato could have had all sorts of reasons for writing in dialogue-form, not least of which could have simply been the tradition of philosophers in Athens in that particular century; to my knowledge, no other philosophical writers in his place and time have been preserved, so we have no idea what his literary context was like. But, perhaps there's some really clever counter to that concern in Roochnik's books, who knows?
Also, tangental thought- the concept of "Talmudic reading" is fascinating, ut are there any works of literature that would justify that sort of confidence?
Philosophers often contradict themselves, or at least apparently contradict themselves. It's also quite possible to misinterpret what a philosopher is actually saying (as you point out people do with respect to Nietzsche). Picking out such contradictions and correcting misunderstandings of other philosophers has been a mainstay of philosophy for a very long time. So to claim that something "obvious" about Plato's teachings is actually not what it at first appears is really par for the course.
In fact, the author seems to address your complaint when he says, "It may well seem that Plato does suggest techne is the best model for moral knowledge. In other words, it may seem that his goal is to establish an expert or authority in the field of the good-bad, just-unjust. Many scholars think this ideal is embodied in the famous "philosopher-rulers" of the Republic. I think these scholars are all wrong, and I wrote a book trying to explain why."
> to my knowledge, no other philosophical writers in his place and time have been preserved, so we have no idea what his literary context was like
We do have surviving works from Aristotle, who studied directly under Plato. He too published some of his writings as dialogues, although he also wrote treatises.
You're right, for some reason I was thinking there was a generation gap there, but it's true that Aristotle did his own teaching also in Athens only a bit later. But I think my point survives, since what we have of Aristotle's works are thought to actually be notes compiled by his students- not intended as finished publications at all. Whether they were released to the public in his time seems to be unknown- there's a story about them being locked in a cellar for a generation before being rediscovered, but apparently that's apocryphal.
Certainly, bright modern-day scholars attributing beliefs to older thinkers that the thinkers themselves outright deny is a thing that happens, and is a healthy part of respectable humanities research. E.g., people who talk about Nietzsche being nihilist or anti-semitic, who left us so many diatribes against nihilists and anti-semites. The humanities wouldn't be interesting if people took their source materials at their word! But its worth keeping in mind how counter-intuitive Roochnik's claims are. (And to his credit, he mentions as much several times.)
I also wonder whether his central piece of evidence, namely that Plato wrote dialogues rather than treatises, isn't projecting relatively-modern writing sensibilities onto an ancient Greek. Plato could have had all sorts of reasons for writing in dialogue-form, not least of which could have simply been the tradition of philosophers in Athens in that particular century; to my knowledge, no other philosophical writers in his place and time have been preserved, so we have no idea what his literary context was like. But, perhaps there's some really clever counter to that concern in Roochnik's books, who knows?
Also, tangental thought- the concept of "Talmudic reading" is fascinating, ut are there any works of literature that would justify that sort of confidence?