Abstract: Fine considers the authenticity of the Peri Idon, the accuracy of Alexander's record of the Peri Idon, the target of the Peri Idon, and finally the date of its composition, relative to Plato's and Aristotle's careers. Fine argues that Aristotle wrote an essay called Peri Idon, and that Alexander reliably reports portions of this essay. The target of the Peri Idon and what Fine will focus upon is Plato, and, in particular, the group of dialogues known as the middle dialogues, rather than other Platonists, or the unwritten doctrines. Fine suggests, tentatively, that the Peri Idon was written while Aristotle was still a member of the Academy, and therefore written before some of Plato's late dialogues, such as Sophist, and Timaeus, but probably after the Parmenides and Theaetetus.

Keywords: Academy Theaetetus, Alexander, authenticity, the middle dialogues, Unwritten doctrines,