Having founded the Academy in c. 388–387 BCE, Plato served as its scholarch (scholarchēs, Diogenes Laertius 5.2.15) until his death in 348–347 BCE. Yet the precise nature of Plato’s intellectual activities during these decades remains elusive. While conjectures abound, it is certain beyond reasonable doubt that he composed the dialogues traditionally attributed to him and engaged in frequent oral exchanges (cf. pollē synousia, Epistle VII, 341c6) with his students. Consider, for instance, Plato’s Socrates speaking to Adeimantos in the Republic: “For you have often heard it said (pollakis akēkoas) that the form of the good is the most important thing to learn about (megiston mathēma)” (Rep. 505a2-3, tr. Grube). Since Adeimantos has not yet heard this from possible oral performances of earlier dialogues, he must have “often heard” this during frequent oral discussions between Plato and him or his students.
In interpreting the dialogues, one may with O’Brien – albeit somewhat anachronistically – distinguish between what might be termed a “Catholic” approach and a “Protestant” approach. The “Catholic” approach maintains that Plato’s teaching is embodied not merely in the written corpus he produced, but also “in the so called unwritten doctrines” attributed to him (en tois legomenois agraphois dogmasin, Aristotle, Physics 2, 209b13–16). This is analogous to the decree of the Council of Trent, which affirmed that the truth concerning Jesus Christ is preserved not only in libris scriptis, but also in sine scripto traditionibus.[1] Conversely, the “Protestant” approach, whose roots lie in Schleiermacher’s Einleitung, is guided by the principle of sola scriptura, recognizing only what is contained in the dialogues as genuinely Platonic.[2]
In contemporary scholarship, there exists a consensus among both “Esotericists” (“Catholics”) and “Anti-Esotericists” (“Protestants”) that the oral tradition attributed to Plato is not simpliciter identical to the content of the dialogues. Its precise nature, relation to the dialogues and philosophical significance continue to be contentious, although the debate has moderated somewhat following the deaths of the most prominent proponents of the schools of Tübingen and Milan, namely Hans Joachim Krämer (1929–2015), Konrad Gaiser (1929–1988), Thomas A. Szlezák (1940–2023), Giovanni Reale (1931–2014) and Maurizio Migliori (1943–2023). Jens Halfwassen (1958–2020), under whom O’Brien studied, was also a significant figure in this tradition. Given that these scholars published their extensive monographs primarily in German or Italian, O’Brien performs a valuable service by making this field of scholarship more accessible to an English-speaking audience, for whom proficiency in these languages is increasingly rare.
The volume is organised into six chapters: 1. “What are the Unwritten Doctrines?”, 2. “Plato’s Criticism of Writing”, 3. “Plato’s Theory of Principles and the Testimonia”, 4. “Consequences of the Tübingen Approach for Later Platonism”, 5. “Critics of the Unwritten Doctrines” and 6. “Conclusion”. The aim of the work is neither to give a comprehensive overview of research in this area nor to propose a novel interpretation. Instead, it serves as an introduction to the salience of these issues and, by extension, the author’s own perspective, which is informed by Halfwassen’s scholarship. Its chief merit lies in tracing the continuity between Plato’s “unwritten doctrines” as reported by Aristotle, its modification in Speusippus and the reappropriation of these themes – particularly that of “the One” – in Plotinus and Proclus, a connection made already by Léon Robin: “Aristotle set us on the path toward a Neoplatonic interpretation of his master’s philosophy.”[3]
However, it must be noted that a significant portion of the relevant literature is overlooked. For instance, the author neglects Yvon Lafrance’s meticulous study on the conclusion of the Phaedrus, which explicitly challenges the Tübingen approach as well as the historical value of the testimonia.[4] Furthermore, the work fails to address the question of why Plato refrained from writing down these “unwritten doctrines” and publishing them in a written form like the dialogues. The possibility that a written account of the principles – and specifically of the Good or the One – could have led to misunderstandings cannot have been the sole deterrent, since an oral transmission or even a public “lecture on the Good” (akroasis peri tagathou, Aristoxenus, Elementa harmonica 2.30) may be just as easily misunderstood as an oral “testament”.[5]
Despite these shortcomings, this monograph provides a valuable stimulus for English-speaking scholars to engage more rigorously with this important, yet frequently neglected field of enquiry.
Notes
[1] Denzinger, Heinrich. Enchiridion symbolorum definitionum et declarationum de rebus fidei et morum. Edited by Peter Hünermann. 45th edition. Freiburg im Breisgau, 2017, § 1501.
[2] Schleiermacher, Friedrich. Einleitung in Platons Werke, Band I des ersten Teils. Berlin, 1804, 3–52
[3] Robin, Léon. La théorie platonicienne des idées et des nombres d’après Aristote : étude historique et critique. Paris 1904, 600, my tr.
[4] Lafrance, Yvon. “La fin du Phèdre de Platon (274b–279c): ésotérisme et antiésotérisme.” Philosophie antique 3, 2003, 81–119, esp. 103.
[5] Cf. Ferber, Rafael. The Ignorance of the Philosopher: Why Did Plato Not Write the “Unwritten Doctrine”? Baden-Baden 2025, 20, 104.