BMCR 2021.10.52

Plato’s “Theaetetus” revisited

, , Plato's "Theaetetus" revisited. Trends in classics. Supplementary volumes, volume 110. Berlin; Boston: De Gruyter, 2020. Pp. xiv, 309. ISBN 9783110715262 $137.99.

[Authors and titles are listed below.]

The Theaetetus has always been a difficult nut to crack among Plato’s corpus. In the dialogue, Socrates poses the question of what knowledge is to a young student of mathematics, Theaetetus (146a–c), and raises three possible definitions of knowledge—as (1) sense perception (αἴσθησις) (151e–187a), (2) true judgment, or opinion (ἀληθὴς δόξα) (187b–201c), or (3) true judgment with an account (ἀληθὴς δόξα μετὰ λόγου) (201d–210a)—before the dialogue ends in aporetic impasse. The work has taken on a multitude of different interpretations, with the majority in the Anglophone sphere tending toward a negative, developmentalist reading (i.e., Plato changed his views on knowledge, after abandoning the middle dialogues’ theory of the Forms), although other readings exist, such as a unitarian reading (e.g., Plato uses the dialogue’s aporetic form as a pedagogical device—not as developing/changing his own views). Other open questions remain, such as why, despite being traditionally classed as a late dialogue, the Theaetetus imitates the form and structure of the early Socratic aporetic dialogues (e.g., Meno), and what the aporiai themselves are supposed to lead to, if they aren’t only negative in purpose (e.g., as an invitation towards the New Academy’s skepticism).

Beatriz Bossi and Thomas Robinson’s edited collection is not addressed to any one specific thesis or theme, but rather brings together a set of contributions that raise new interpretations on various aspects and parts of the Theaetetus. The book is the result of the Third International Spring Plato Seminar (May 21–22, 2018) in Madrid, Spain, after two previous seminars on the Sophist (2009) and Statesman (2016)—apt background for this set of studies on the Theaetetus. The editors divide the chapters into sections loosely mirroring the Theaetetus’ own structure (see below), effectively setting the stage for the themes discussed.

In Part I, David Sedley’s contribution, on Plato’s self-references, is effectively an addendum to his 2004 book[1] on Theaetetus’ Socrates as a “midwife” for Plato’s own philosophy, where he traces Plato’s implicit self-references in this capacity into other dialogues, such as the Republic, Charmides, Timaeus, and so on. Michel Narcy builds on this theme by showing how the Theaetetus reveals a new Socrates in contrast to the Socrates of earlier dialogues (e.g., Euthyphro or Meno): despite Socrates’ claim of merely being a midwife, yet not knowing anything himself. Narcy argues[2] that the lack of the language of “midwife” in the dialogue’s second half (185e ff.) demonstrates Socrates’ maieutic method—particularly where the discussion of false judgment in the last two definitions (cf. above) hints at the Sophist. Perhaps in subtle contrast to Sedley, Narcy argues that Plato doesn’t have Socrates reveal his positive teaching, the way that Sophist’s Athenian Stranger does, not because Socrates himself is without the ability to, but rather because Theaetetus himself isn’t ready at that point (pp. 18–19)—in contrast to the Sophist, when he is.

In Part II, Graciela Marcos de Pinotti’s contribution, on Plato’s methodological strategy in the first definition’s discussion (151d–186a), looks at the Theaetetus as a bridge between the early dialogues (in terms of their aporetic character and absence of the Forms) and the later dialogues (in terms of discussing knowledge, the physical world, and becoming). One insightful aspect of her argument is that Plato’s strategy in this first part reveals that language, rather than attempting to explicate the nature of things, is in itself constrained by the nature of things: hence it is not merely the theory of flux, but rather in its explication in the dialogue, that shows the absurdities one runs into. For De Pinotti, the criticism of universal flux is constructive, insofar as it paves the way for a conception of Being that includes both changing and unchanging entities—pointing forward to the Sophist (similar to Narcy’s reading). In turn, Álvaro Vallejo Campos in his contribution reads the Theaetetus as functioning in parallel with Aristotle’s Topics, where refutation (ἔλεγχος) plays an essential role in dialectic, i.e., in testing the premises of different positions and revealing absurdities where they arise. Although the Theaetetus is similar to the early dialogues in their destructive use of ἔλεγχος, ἔλεγχος in the Theaetetus takes on a more positive role in refining and ascending through the proposed definitions of knowledge—similar to Aristotle’s own use of ἔλεγχος in dialectic in both the Topics and Sophistical Refutations (e.g., pp. 37, 39). In this regard, Campos very interestingly observes that Aristotle’s Topics “gives us a testimony of a common practice of dialectic in the Academic tradition that lends plausibility to interpreting the Theaetetus in light of it” (p. 48).

In Part III, Francisco Lisi attempts to highlight the distinctly Platonic—rather than Protagorean, Heraclitean, or Cyrenaic (pp. 56–60)—character of the theory of flux in 155d1–160e4, which Socrates eventually rejects as a model for knowledge, though not—as Lisi argues—a refutation of universal flux in itself. In support of this, Lisi points to Timaeus 49c–e (pp. 63–64), where nothing remains stable in the receptacle (ὑποδοχήν), but what is becoming is in constant change—much of which parallels the language of Tht. 159e–160c, which seems to support her claim of Plato’s theory of perception (despite the critical context). Beatriz Bossi in her contribution focuses on Theaetetus’ initial claim for the first definition and argues that Socrates rejects only the views of his predecessors that he manipulatively attaches to Theaetetus’ initial claim—but not Theaetetus’ claim in itself. For Bossi, Theaetetus is trying grasp a notion of αἴσθησις broader in meaning than mere “sense” perception (p. 68), which Socrates otherwise seems to ignore. Despite what seems to be almost a sophistic ploy, Bossi sees this as Socrates “vaccinating” Theaetetus against false positions he would otherwise be tempted by—agreeing well with Narcy’s paper.

Franco Trabattoni goes over the very well-known self-refutation (περιτροπή) argument against Protagoras in 171a, where he sees Protagoras’ position (namely, “all opinions are true”) as held, not simply as one opinion among all others, but rather as an absolute truth; for Trabattoni this can only explain why Plato continues his critique after 171a, showing that (1) Protagoras cannot avoid self-refutation, and, more definitively, (2) “he cannot maintain that all we have are doxai” (p. 105). Marcelo Boeri in his contribution pushes back against the scholarship’s tendency to read the dialogue as about epistemology alone, apart from metaphysics or other disciplines (pp. 107–109), and, though discussed in a rather wide-ranging way, argues that Plato remains concerned with the practical, alongside theoretical, consideration of knowledge, and, more interestingly, that Plato follows Protagoras’ relativist position, at least in some regard: for instance, when Plato claims that “no one can know better than oneself what oneself is perceptually experiencing when oneself is experiencing it (Tht. 160c4–9)” (p. 110–111). This suggests that the “knowledge” sought in the Theaetetus, for Boeri,[3] is broader than just descriptive items, including both non-perceptible and perceptible items (p. 129). Finally, Xavier Ibáñez-Puig’s essay looks at the metaphors of taste and food in the dialogue, as background to the characters and how they reflect their respective philosophical position, both of which are foundational for the philosophy of education that the dialogue puts forward, both for Theaetetus and the reader.

In Part IV, Thomas Robinson discusses the notion of the soul in Theaetetus, linking concepts discussed in a dialectical context, like the metaphor of the aviary and the wax tablet in the soul, to other dialogues which directly deal with the soul (e.g., Phaedrus, Phaedo, Timaeus, etc.). In the final pages he offers his own dating of the Theaetetus as a more “negative” conclusion and transition, after the Timaeus and Phaedrus, in Plato’s development. Carolina Araújo in her chapter critiques previous scholars’ Aristotelian interpretations of disposition in the soul in the example of the coat and the aviary model (195c–200d), where Plato discusses the soul’s acquisition of an item (either the coat or bird in the aviary) and its power of choice to use or not use the item. Araújo argues that, whereas Aristotle speaks of the soul’s rational power for opposites (e.g. Metaphysics Θ.2, 1046b1–12)—implying productive knowledge, aimed at the state of the external objects—Plato’s metaphor implies the internal “mind content”, affecting the state of the user and not that of the external object (pp. 162–163). One difficulty I found in Araújo’s argument was her claim in p. 167 that Aristotle’s “objects of thought are individuals, and not kinds or rules for specification”. Yet this is not entirely clear: the object of thought, per De Anima III.4 (429a15–16, 28), is the form, which may correlate either with an individual or a universal—i.e., it could also match the “kinds or rules for specification” that Plato references. Without clarifying this point, it was somewhat hard to see how strongly to distinguish Aristotle’s position from Plato’s with the wax tablet model—though Araújo’s general argument otherwise seems fair.

Francisco Gonzalez addresses a common issue in scholarship on the Theaetetus and Plato’s other dialogues: why does dialectic require dialogue for Plato? Despite tendencies to reduce dialogue to individual dialectic (as, e.g., in Hegel), Gonzalez shows how Plato brings out the necessity for the dialogue form as the measure of philosophical investigation in the Theaetetus, for instance in lieu of a judge or a given criterion of truth (pp. 182–183). This leads to Gonzalez’s intriguing conclusion that the third, last definition of knowledge—despite its failure—implies a positive final response for the Theaetetus: the exchange of logoi in dialoguing is what helps to lay aside false belief—a positive sign of progress—as seen in the three definitions’ refutation in dialogue (pp. 188–189). In turn, Franco Ferrari in his contribution, while conceding alongside Charles Kahn[4] that the Sophist provides the satisfactory answer to Theaetetusaporia on knowledge, attempts to show how the dialogue already contains its euporia within its aporetic frame. Ferrari sees this particularly in the discussion of the final definition, when Socrates suggests a distinction between the “all” (πᾶν) and “whole” (ὅλον), where the former implies identity with the parts, while the latter implies a relation to the parts—yet a distinct unity irreducible to the parts’ sum (203e–204a). Yet despite Socrates’ ultimate rejection of this model—based on “anti-Platonic assumptions and fallacious arguments”—this already directly points the way to the Sophist’s model (pp. 202–203), where the objects of knowledge are “one” ontologically, yet predicatively “many” (cf. Soph. 251b; p. 204)—fulfilling the Theaetetus’ criterion for the definition of knowledge.

Finally Part V, features a thorough, especially philological discussion on aspects of the dialogue’s reception history, both proximately within Plato’s Academy and later into the Roman and Byzantine eras. Claudia Mársico argues that the Theaetetus, especially in the dream sequence (201d–202d), is witness to the relationship between Antisthenes and Plato, reflecting an inner-school polemic between Socratics of this period. Harold Tarrant details the wording of different passages in the dialogue that show their formative influence in the New Academy’s skeptical position and the use of suspense of judgment. Tarrant also shows that the phrasing of these passages implies that the Theaetetus has more in common with the Cratylus and Meno, suggesting more of a Protagorean influence than a skeptical one on epistemology. One wishes Tarrant could elaborate further on the philosophical consequences of this, yet his detailed textual analysis proves very useful. In the last chapter, Michele Curnis analyzes the textual tradition of the Theaetetus and the influence of parts of the dialogue in the school programs of late antiquity and the Byzantine era—especially the λόγος μείζων (“bigger speech”) of 172b–c, pointing to the portrait of the philosopher and his inadequacy in civil and political situations. Curnis’ observation is particularly intriguing that, despite the epistemological angle the New Academy takes on the Theaetetus, late antique and Byzantine readers would follow the anonymous commentator of the dialogue in focusing on the dialogue’s political angle, with passages like the λόγος μείζων.

Overall, I found this book’s contributions to be solid and of high quality. Among others, I found Ferrari’s and Narcy’s papers to be the most interesting in trying to assess the Theaetetus as a whole in relation to the Sophist—though all the others stand equally strong. Typographical errors were very rare, and the style of writing was overall clear and straightforward. Although addressed to individual aspects, the contributions in this book are an important benchmark, and worth further study, for current and future work on the Theaetetus.[5]

Authors and titles

Part I: On Stage and Behind the Scene
David Sedley: “Plato’s Self-References” (pp. 3–10)
Michel Narcy: “The Old and the New Socrates in the Theaetetus” (pp. 11–20)
Part II: Method
Graciela E. Marcos de Pinotti: “On Plato’s Methodological Strategy (Theaetetus 151d–186e): From Hypothesis to Self-Refutation” (pp. 23–33)
Álvaro Vallejo Campos: “Dialectic in the Theaetetus” (pp. 35–49)
Part III: Subject and Object of Perception in the Flux
Francisco Lisi: “Heraclitus, Protagoras and Plato: Theaetetus 155d1–160e4” (pp. 53–64)
Beatriz Bossi: “On Socrates’ Manipulative Dealing with Theaetetus’ First Claim about Knowledge” (pp. 65–88)
Franco Trabattoni: “Peritrope Once Again” (pp. 89–106)
Marcelo D. Boeri: “Platonic Epistemology and the Internalist-Externalist Debate” (pp. 107–129)
Xavier Iáñez-Puig: “‘We Are What We Eat’: The Theaetetus as a Philosophy of Education” (pp. 131–145)
Part IV: Knowledge and Thinking
Thomas M. Robinson: “Soul in Theaetetus” (pp. 149–158)
Carolina Araújo: “Disposition in the Aviary Model” (pp. 159–172)
Francisco J. Gonzalez: “Thinking as Conversation in Plato’s Theaetetus” (pp. 173–192)
Franco Ferrari: “Traces of Euporia in an Aporetic Dialogue: Relational Ontology in Plato’s Theaetetus” (pp. 193–205)
Part V: The Reception
Claudia Mársico: “Intra-Socratic Polemics in Plato’s Theaetetus: Antisthenes and the Dream Theory” (pp. 209–223)
Harold Tarrant: “The Theaetetus as a First Step on the Path to a New Academy” (pp. 225–249)
Michele Curnis: “The Textual Tradition of the Theaetetus from Stobaeus to the Medieval Anthologies” (pp. 251–276)


[1] See David Sedley, The Midwife of Platonism: Text and Subtext in Plato’s “Theaetetus” (Oxford: Oxford University Press, 2004).

[2] Against Myles Burnyeat, “Socratic midwifery, Platonic inspiration” Bulletin of the Institute of Classical Studies 24 (1977) 7–16, on p. 17.

[3] Following Myles Burnyeat, The “Theaetetus” of Plato (Indianapolis/Cambridge: Hackett, 1990).

[4] See Charles Kahn, “Why is the Sophist a Sequel to the Theaetetus?”, Phronesis 52 (2007) 33–37,×177959.

[5] The reviewer would like to express his gratitude to the European Research Council for its support within the framework of the project, “Neoplatonism and Abrahamic Traditions” (ERC_CoG_771640).