Friedrich Schleiermacher, who played a major role in the modern study of Plato, rejected the notion of a Platonic oral tradition, arguing that Plato’s central purposes were expressed in his dialogues. Though Friedrich Nietzsche was heavily critical of Schleiermacher’s interpretation, Schleiermacher’s became the dominant view especially in the Anglo-American academy. American Harold Cherniss went so far as to say that Aristotle was simply mistaken when he referenced Plato’s “so-called unwritten doctrine.”
The Tübingen school, or a group of scholars at Tübingen University who study the issue, pushed back against Schleiermacher, by not only pointing out Plato’s over references in the Phaedrus and in letter 7 but also noting the numerous times that Socrates refers to things he cannot talk about throughout Plato’s dialogues. As Dmitri Nikulin puts it, “The Tübingen interpretation to a large extent suspends the fundamental principle of modern hermeneutical interpretation: the sola scriptura. This hermeneutical principle stresses the importance of going back to the ‘original’ text as the only source of dependable interpretation, and hence implies the rejection of any oral tradition of transmission that is construed as only secondary and therefore untrustworthy.”
The Tübingen scholars have set about trying to recover what the unwritten doctrine might have been by looking at clues in Plato’s dialogues and statements by his pupils, to argue that the unwritten doctrines seem to relate to mathematical relations of ultimate reality, and dualism and monism. Many argue that the Neoplatonist’s “One” may have been what Plato had in mind, and that Plotinus had it right.
At the same time, not only did quite a bit of time pass between Plato and Plotinus but Plotinus’s teacher, Ammonius Saccus, was a Christian. Ammonius also taught Origen, who, in repose to Christian critic Celsus’s claim that Christian were too secretive, said Jesus “saw better than Plato … what things were to be committed to writing, and how this was to be done, and what was by no means to be written to the multitude, and what was to be expressed in words, and what was not to be so conveyed.” Origen seemed to be suggesting that the things that Jesus kept secret were somehow related to Plato.
There do seem to be a lot in interesting connections between Plato’s and Jesus’s unwritten doctrines, which will be the theme of the posts that follow.
 Hans Joachim Krämer, “Plato’s Unwritten Doctrine,” in The Other Plato: The Tübingen Interpretation of Plato’s Inner-Academic Teachings, ed. Dmitri Nikulin (Albany: State University of New York, 2012), 67-69.
 Dmitri Nikulin, “Testimonia Et Fragmenta,” in The Other Plato: The Tübingen Interpretation of Plato’s Inner-Academic Teachings, ed. Dmitri Nikulin (Albany: State University of New York, 2012), 2,7. Cherniss was the pupil of Paul Shorey at Princeton who was a major advocate for the “unitarian” interpretation of Plato, or “that Plato always defended a single, coherent metaphysical system throughout his career.” Says John Dillon, Aristotle “knew what he was talking about in each instance (to assume otherwise, as Harold Cherniss and his followers are driven to do, is quite absurd.)” Dillon, Heirs of Plato, 17. Dillon is Irish, and therefore apparently not part of the Anglo-American (ie Protestant) view that rejects the unwritten doctrine.
 Krämer, “Plato’s Unwritten Doctrine.” Krämer list of references to higher ideas that cannot be discussed include Prot. 356E8– 357C1; Meno 76E3– 77B1; Phaedo 107B4– 10; Rep. 506D2– 507A2, 509C1– 11; Parm. 136D4– E3; Soph. 254B7– D3; Polit. 284D1f.; Tim. 28C, 48C, 53D; Legg. 894A.
 Dmitri Nikulin, “Testimonia Et Fragmenta,” 8.
 Krämer, “Plato’s Unwritten Doctrine.”
 Origen, Contra Celsus, 6.6.