One of these distributions was into Tetralogies, or groups of four each. This was in substitution for the Trilogies introduced by Aristophanes or by Kallimachus, and was founded upon the same dramatic analogy: the dramas, which contended for the prize at the Dionysiac festivals, having been sometimes exhibited in batches of three, or Trilogies, sometimes in batches of four, or Tetralogies — three tragedies, along with a satirical piece as accompaniment. Because the dramatic writer brought forth four pieces at a birth, it was assumed as likely that Plato would publish four dialogues all at once. Without departing from this dramatic analogy, which seems to have been consecrated by the authority of the Alexandrine Grammatici, Thrasyllus gained two advantages. First, he included ALL the Platonic compositions, whereas Aristophanes, in his Trilogies, had included only a part, and had left the rest not grouped. Thrasyllus included all the Platonic compositions, thirty-six in number, reckoning the Republic, the Leges, and the Epistolæ in bulk, each as one — in nine Tetralogies or groups of four each. Secondly, he constituted his first tetralogy in an impressive and appropriate manner — Euthyphron, Apology, Kriton, Phædon — four compositions really resembling a dramatic tetralogy, and bound together by their common bearing, on the last scenes of the life of a philosopher.[45] In Euthyphron, Sokrates appears as having been just indicted and as thinking on his defence; in the Apology, he makes his defence; in the Kriton, he appears as sentenced by the legal tribunal, yet refusing to evade the sentence by escaping from his prison; in the Phædon, we have the last dying scene and conversation. None of the other tetralogies present an equal bond of connection between their constituent items; but the first tetralogy was probably intended to recommend the rest, and to justify the system.
[45] Diog. L. iii. 57. πρώτην μὲν οὖν τετραλογίαν τίθησι τὴν κοινὴν ὑπόθεσιν ἔχουσαν· παραδεῖξαι γὰρ βούλεται ὅποιοις ἂν εἴη ὁ τοῦ φιλοσόφου βίος. Albinus, Introduct. ad Plat. c. 4, p. 149, in K. F. Hermann’s Append. Platon.
Thrasyllus appears to have considered the Republic as ten dialogues and the Leges as twelve, each book (of Republic and of Leges) constituting a separate dialogue, so that he made the Platonic works fifty-six in all. But for the purpose of his tetralogies he reckoned them only as thirty-six — nine groups.
The author of the Prolegomena τῆς Πλάτωνος Φιλοσοφίας in Hermann’s Append. Platon. pp. 218-219, gives the same account of the tetralogies, and of the connecting bond which united the four members of the first tetralogical group: but he condemns altogether the principle of the tetralogical division. He does not mention the name of Thrasyllus. He lived after Proklus (p. 218), that is, after 480 A.D.
The argument urged by Wyttenbach and others — that Varro must have considered the Phædon as fourth in the order of the Platonic compositions — an argument founded on a passage in Varro. L. L. vii. 37, which refers to the Phædon under the words Plato in quarto — this argument becomes inapplicable in the text as given by O. Müller — not Varro in quarto but Varro in quattuor fluminibus, &c. Mullach (Democriti Frag. p. 98) has tried unsuccessfully to impugn Müller’s text, and to uphold the word quarto with the inference resting upon it.
Philosophical principle — Dialogues of Search — Dialogues of Exposition.
In the other distribution made by Thrasyllus,[46] Plato was regarded not as a quasi-dramatist, but as a philosopher. The dialogues were classified with reference partly to their method and spirit, partly to their subject. His highest generic distinction was into:—1. Dialogues of Investigation or Search. 2. Dialogues of Exposition or Construction. The Dialogues of Investigation he subdivided into two classes:—1. Gymnastic. 2. Agonistic. These were again subdivided, each into two sub-classes; the Gymnastic, into 1. Obstetric. 2. Peirastic. The Agonistic, into 1. Probative. 2. Refutative. Again, the Dialogues of Exposition were divided into two classes: 1. Theoretical. 2. Practical. Each of these classes was divided into two sub-classes: the Theoretical into 1. Physical. 2. Logical. The Practical into 1. Ethical. 2. Political.
[46] The statement in Diogenes Laertius, in his life of Plato, is somewhat obscure and equivocal; but I think it certain that the classification which he gives in iii. 49, 50, 51, of the Platonic dialogues, was made by Thrasyllus. It is a portion of the same systematic arrangement as that given somewhat farther on (iii. 56-61), which is ascribed by name to Thrasyllus, enumerating the Tetralogies. Diogenes expressly states that Thrasyllus was the person who annexed to each dialogue its double denomination, which it has since borne in the published editions — Εὐθύφρων — περὶ ὁσίου — πειραστικός. In the Dialogues of examination or Search, one of these names is derived from the subject, the other from the method, as in the instance of Euthyphron just cited: in the Dialogues of Exposition both names are derived from the subject, first the special, next the general. Φαίδων, ἢ περὶ ψυχῆς, ἠθικός. Παρμενίδης, ἢ περὶ ἰδεῶν, λογικός.
Schleiermacher (in the Einleitung prefixed to his translation of Plato, p. 24) speaks somewhat loosely about “the well-known dialectical distributions of the Platonic dialogues, which Diogenes has preserved without giving the name of the author”. Diogenes gives only one such dialectical (or logical) distribution; and though he does not mention the name of Thrasyllus in direct or immediate connection with it, we may clearly see that he is copying Thrasyllus. This is well pointed out in an acute commentary on Schleiermacher, by Yxem, Logos Protreptikos, Berlin, 1841, p. 12-13.
Diogenes remarks (iii. 50) that the distribution of the dialogues into narrative, dramatic, and mixed, is made τραγικῶς μᾶλλον ἢ φιλοσόφως. This remark would seem to apply more precisely to the arrangement of the dialogues into trilogies and tetralogies. His word φιλοσόφως belongs very justly to the logical distribution of Thrasyllus, apart from the tetralogies.