1. Plato, Theaetetus 167 B-C: I [Protagoras] says… that the wise and good orators make the good, instead of the evil, seem to be right to their states. For I claim that whatever seems right and honorable to a state is really right and honorable to it, so long as it believes it to be so; but the wise man causes the good, instead of that which is evil to them in each instance, to be and seem right and honorable.
But Plato Phaedrus 273E: ‘The wise must consider the art of speaking not for the sake of speaking and negotiating with people, but for the sake of being able to say things pleasing to the gods and doing everything pleasantly as far as one can. For, Tisias, a reasonable person should not practice pleasing our fellow slaves – as those wiser than us say – except as a byproduct, but practice pleasing good masters who are from good parents.’ Compare to this Philod. Rhet. 2.92, fr. 21.5 (if it is restored correctly): ‘He says the goal is to persuade the listener, whom one may well call a master’.
2. Plato, Protagoras 318E-319A: That learning consists of good judgement in his own affairs, showing how best to order his own home; and in the affairs of his city, showing how he may have most influence on public affairs both in speech and in action… (Socrates:) You appear to be speaking of the civic science, and undertaking to make men good citizens.
3. Plato, Republic 600C-D: Protagoras of Abdera and Prodicus of Ceos and many others are able to impress upon their contemporaries, while meeting with them privately, the conviction that they will not be capable of governing their homes or the city unless they put them in charge of their education.
4. Plato, Phaedrus 267C (after speaking about Polus): Were there not some similar inventions of Protagoras, Socrates? (Socrates:) Yes, my boy, correctness of diction, and many other fine things.
It is worth noting that Philodemus in the fourth book of his Rhetoric attacks the author who ascribes ‘speaking right’ mainly to the education of rhetoricians (1. P. 190.23 S.); ‘He adds the examples of flawed speech and calls the avoidance thereof “speaking right”’ (192.12). You have here Protagoras or a member of his school, perhaps Demetrius of Phalerum, cf. p. 192.1 and 346 col. 47.
5. Hermias p. 239.14: There is such a thing as correct wording, that is, using the proper terms. Protagoras, for instance, would attend to speech by means of proper vocabulary instead of using comparisons and epithets.
6. Aristotle, Rhetoric 1407b6: The fourth rule (of speaking Greek) consists in keeping the genders distinct—masculine, feminine, and neuter, as laid down by Protagoras; these too must be properly assigned.
7. Aristotle, Sophistic Refutations 137b17: (Making grammatical errors) means to be doing this or appear to be while not doing it or appear not to be while actually doing it, as Protagoras says, if menis and pelex are masculine. For the poet who says oulomenen is erring according to him, but not in everybody else’s opinion, whereas whoever says oulomenon seems to be erring but is not.
Cf. B XXXV 4.
8. Aristophanes, Clouds 658-79:
Soc. But you must learn other things before these; namely, what quadrupeds are properly masculine.
Strep. I know the males, if I am not mad: krios, tragos, tauros, kuon, alektryon.
Soc. Do you see what you are doing? You are calling both the female and the male alektryon in the same way.
Strep. How, pray? Come, tell me.
Soc. How? The one with you is alektryon, and the other is alektryon also.
Strep. Yea, by Neptune! How now ought I to call them?
Soc. The one alektryaina and the other alektor.
Strep. Alektryaina? Capital, by the Air! So that, in return for this lesson alone, I will fill your kardopos full of barley-meal on all sides.
Soc. See! See! There again is another blunder! You make kardopos, which is feminine, to be masculine. […] 677 How ought I to call it henceforth?
Soc. How? Call it kardope, as you call Sostrate.
Strep. Kardope in the feminine?
Soc. For so you speak it rightly.
Aristophanes had already used a joke like this in Knights 969, and he repeats it in Wasps 466; thus it seems that, as those three comedies stem more or less from the same time, that was the very time when Protagoras published his views on grammar. I do not know, however, whether Anaximenes p. 62.19 H. (on clarity) has the same origin: ‘That one must pay attention to the articles, see from the following example: “This human being has done wrong to that human being.” With articles the meaning is clear, without them it is not. Sometimes the opposite is true.’ What he means by this is that anthropos anthropon could also be understood as “this woman that woman.” Varro, The Latin Language 10.2.8: ‘Words closer to each other be in kind often lead to errors, as in the case of nemus and lepus appearing to be similar because they both have the same nominative ending. But they are not similar: to be so they need to have certain similarities, among which is the same grammatical gender. This is not the case here: lepus is masculine and nemus is neuter, for we say hic lepus, but hoc nemus.’ See also Wendland p. 45 and Usener’s learned disquisitions in Quaest. Anaxim. p. 39 f. (Kl. Schr. I 30f.).
9. Plato, Cratylus 391B: (Socrates:) The best way to investigate [about the correctness of the word choice], my friend, is with the help of those who know; and you make sure of their favor by paying them money. They are the sophists, from whom your brother Callias got his reputation for wisdom by paying them a good deal of money. But since you have not the control of your inheritance, you ought to beg and beseech your brother to teach you the correctness which he learned of Protagoras about such matters. – (Hermogenes:) It would be an absurd request for me, Socrates, if I, who reject the Truth by Protagoras altogether, should desire what is said in such a Truth, as if it were of any value.
‘About such matters' seems to refer generically to grammatical issues.
10. Diogenes Laertius 9.53: he was the first to divide speech into four parts: prayer, interrogation, response, exhortation. Others divide it into seven parts: narrative, interrogation, response, exhortation, report, prayer, appellation, which he also calls the pillars of speech.
11. Suda s.v. Protagoras: He was the first to divide all of language into four elements: prayer, interrogation, response, command. After him others divided it into four parts: exposition, interrogation, response, command, announcement, prayer and appellation.
12. Quintilian 3.4.9: Anaximenes wanted the judicial and the deliberative to be the general parts (of the art of speech) and for there to be seven species: persuasion, dissuasion and so on… (10) I shall pass over Protagoras, who thinks that with regard to parts there are only interrogation, response, command, and praying, which he calls eukhole.
Cf. Lucian, Fugitives 10 and on Alcidamas see below B XXII 8.
13. Aristotle, Poetics 1456 b8: Under the head of Diction one subject of inquiry is the various modes of speech, the knowledge of which is proper to elocution or to the man who knows the master art—I mean for instance, what is a command, a prayer, a statement, a threat, question, answer, and so on. The knowledge or ignorance of such matters brings upon the poet no censure worth serious consideration. For who could suppose that there is any fault in the passage which Protagoras censures, because Homer, intending to utter a prayer, gives a command when he says, "Sing, goddess, the wrath"? To order something to be done or not is, he points out, a command. So we may leave this topic as one that belongs not to poetry but to another art.
Cf. B III 10. Friedel. Dissert. phil. Hal. I 139.
14. Plato, Protagoras 338e-339a: I consider, Socrates, that the greatest part of a man's education is to be skilled in the matter of verses; that is, to be able to apprehend, in the utterances of the poets, what has been rightly and what wrongly composed.
15. Plutarch, Pericles 36.3 (Stesimbrotos frag. 11 FHGr II 56): For instance, a certain athlete had hit Epitimus the Pharsalian with a javelin, accidentally, and killed him, and Pericles, Xanthippus said, squandered an entire day discussing with Protagoras whether it was the javelin, or rather the one who hurled it, or the judges of the contests, that ‘in the strictest sense’ ought to be held responsible for the disaster.
The question relates to plausibility (eikos); Diels points to Antiphon’s Tetralogy 2.
16. Aristotle, Rhetoric 2.25.11 1402a24-28: [After Aristotle explains "apparent probability" and that the art of Corax is based on it, he continues:] And this is what “making the weaker the stronger logos” means. For this reason people were justly disgusted with the promise of Protagoras; for it is a lie; (it is) not a real but an apparent probability, (which is) not found in any art except rhetoric and eristic.
Cf. Aristoph. Clouds 112-3, 883-4, Plat. Apol. 18B & 19B-C, Xen. Oec. 11.25, Cic. Brut. 7.30. Kowalski p. 53 f. notes ‘the Protagorean narrative’. Cf. Eur. Supp.486-93, Phoen. 559-60.
17. Stephanus of Byzantium, s.v. Abdera: … Protagoras, who Eudoxos reports made a position stronger or weaker and taught his students how to blame and praise the same person.
Philod. On Rhetoric I p. 214, Col. XXXIIa 25: ‘If the sophists – and they alone […] say that the entire thing has the ability to praise as well as criticize, it is worth asking whether they think it the same to perform an encomium, when they want to, and to criticize, when they so decide…’
18. Seneca, Letters 88.43: Protagoras claims that one can argue both sides of any issue equally well, and also over the issue of whether every issue can be argued over on both sides.
19. Diogenes Laertius 9.51: And he was the first to say that there are two logoi, on every matter, opposed to each other; to which he was also the first to pose a series of questions after doing this.
Cf. Clement of Alexandria 2.464.14 St., Jaeneke 19-20 The books by Protagoras on ‘the two antilogies’ are quoted by Diog. Laert. 9.55. Nestle 289f.
20. Diogenes Laertius 9.53: He was the first to demonstrate dialectical approaches to a given subject, as reported by the dialectician Artemidoros in Against Chrysippos.
Philod. On Rhet. I p. 206, 17, after discussing those who claimed that an orator could speak about anything: ‘And there is not even anything in their treatises that fits matters other than political questions. For what they say about topical questions, while very pleasant to deal with, does not belong in the present inquiry.’
Quint. 3.5.5: ‘There are endless questions that are addressed under abstraction from the specific characters, time, place and the like, which the Greeks call thesis.’ Cf. Theon Prog. p. 120 Sp.
21. Cicero, Brutus 12.46: (In the synagoge technon Aristotle says that) Protagoras wrote and provided disputations on famous subjects, which are now called “common places”.
E. Maass, Hermes 22, 586 f. tries to reconstruct such a disputation about the state from some fragmentary sources and to attribute it to Protagoras.
22. Quintilian, Institutions 3.1.2: Among these, the first to deal with “topics” were allegedly Protagoras and Gorgias; with affects, Prodicus, Hippias, Protagoras himself and Thrasymachus.
23. Plato, Protagoras 334e-335b: Well, for instance, I have heard, I said, that you yourself are able, in treating one and the same subject, not only to instruct another person in it but to speak on it at length, if you choose, without ever being at a loss for matter; or again briefly, so as to yield to no one in brevity of expression. So, if you are going to argue with me, employ with me the latter method, that of brevity. […] For you—as people relate of you, and you yourself assert—are able to hold a discussion in the form of either long or short speeches.
Cf. Prot. 329B, 334D, Dialexeis 8.1. Plato, Phaedrus 267B calls it (conciseness of words) syntomia logon, cf. Euripides Aeolus fr. 28: ‘Children of a capable man, who can summarize long speeches in a well-spoken short one.’
24. Diogenes Laertius 9.52: He was the first to divide time into parts and to expound the meaning of the instant; he also first engaged in rhetorical battles, lobbed sophisms at those who argued facts and addressed words without caring about their meaning.
Jaeneke p. 19 f. explains how these words relate to rhetoric. See also C. P. Gunning, De sophistis Graeciae praeceptoribus (Amsterdam 1915) 112-3 and on Gorgias see below p. 47-8.
25. Stobaeus, Anthology 3.29.80: Protagoras said that there is no value either in art without practice or in practice without art.
Cf. what follows, Isocr. 15.187-8, Plato Phaedr. 269D, Philodemus I p. 49.1-2.
26. Anecdota Parisina 1, p. 171, 31: In his so titled “Great Speech” Protagoras says: “Learning requires both talent and practice,” and: “One must begin to learn from a young age.”
Cf. Plato Prot. 323 C f., Isocr. 15.180-1. W. Schmid, Gesch. d. gr. Lit. III 1 p. 23 n. 2.
27. Plato, Protagoras 318a: Young man, you will gain this by coming to my classes, that on the day when you join them you will go home a better man, and on the day after it will be the same; every day.
Cf. ibid. 319 A. Usener (Quaest. Anaxim. 42) points out that the eristic sophists lay claim to this ability and Isocrates also brags about it (13.3-4, 13.21, 15.84-5); he also refers to Anaximenes, who in the final chapter of his treatise teaches how to live one’s life so as to gain a positive reputation to help one persuade people. Quintilian too sets out, at the end of his very extensive work about the training of an orator, to prove that he must be a good person. More on this subject in RhM 54, 285-6.