There are two passages in Republic III that elucidate Polemarchus’ performance in Republic I and in the Phaedrus. The first is as follows: ‘As for the man of orderly life (Ho men moi dokei metrios anȇr), when the time comes to describe some saying or action of another good man (epeidan aphikȇtai en tȇi diȇgȇsei epi lexin tina ȇ praxin andros agathou), – I think he will be willing to personate him (ethelȇsein hȏs autos ȏn ekeinos apangellein) … But when he comes to a character which is unworthy of him (hotan de gignȇtai kata tina heautou anaxion), he will not seriously assume the likeness of his inferior (ouk ethelȇsein spoudȇi apeikazein heauton tȏi cheironi), and will do so, if at all, for a moment only (ei mȇ kata brachu) when he is performing some good action (hotan ti chrȇston poiȇi).’ (396c5-d5, tr. Jowett)
Polemarchus’ discussion on justice in Republic I comprises in its totality slightly less than four and a half Stephanus pages, from 331d4 to 336a8. In comparison, the discussion with the sophist Thrasymachus takes eighteen Stephanus pages, from 336b1-354a11, and the discussion of Socrates with Plato’s brothers Adeimantus and Glaucon takes 264 Stephanus pages, from 357a1 to 621d3.
Polemarchus in that short discussion does, or rather Socrates compels him to do, something good: he gives up his and his father’s concept of justice.
This first passage elucidates Polemarchus’ position in the Phaedrus only indirectly, it indicates that when Plato wrote the dialogue, he was mistaken about him.
The second passage sheds light on the mistake Plato made in the Phaedrus. Speaking of how to choose the best physicians and judges, Socrates says: ‘Now the most skilful physicians will be those (Iatroi men deinotatoi an genointo) who, from their youth (ei ek paidȏn arxamenoi), besides learning their art (pros tȏi manthanein tȇn technȇn), have had an extensive acquaintance with disease in its direst forms (hȏs pleistois te kai ponȇrotatois sȏmasin homilȇseian); and who, instead of having a flawless constitution, have themselves suffered from all manners of diseases (kai autoi pasas nosous kamoien kai eien mȇ panu hugieinoi phusei) … But with the judge it is otherwise (Dikastȇs de ge), since he governs mind by mind (psuchȇi psuchȇs archei); he ought not therefore be to have been trained among vicious minds, and to have associated with them from youth upwards (hȇi ouk enchȏrei ek neas en ponȇrais psuchais tethraphthai te kai hȏmilȇkenai), and to have gone through the hole calendar of crime (kai panta adikȇmata autȇn ȇdikȇkuian diexelȇluthenai), only in order that he may quickly infer the crimes of others as he might their bodily diseases from his own self-consciousness (hȏste oxeȏs aph’ hautȇs tekmairesthai ta tȏn allȏn adikȇmata hoion kata sȏma nosous); the honourable mind which is to form a healthy judgement should have had no experience or contamination of evil habits when young (all’ apeiron autȇn kai akeraion dei kakȏn ȇthȏn nean ousan gegonenai, ei mellei kalȇ k’agathȇ ousa krinein hugiȏs ta dikaia). And this is the reason (dio dȇ kai) why in youth good men often appear to be simple (euȇtheis neoi ontes hoi epieikoi phainontati), and are easily practised by the dishonest (kai euexapatȇtoi hupo tȏn adikȏn)), because they have no example of what evil is in their own souls (hate ouk echontes en heautois paradeigmata homoiopathȇ tois ponȇrois).’ (408d10-409b2, tr. Jowett)
Having insinuated himself into Plato’s mind as a man turned to philosophy, a man whose memory was carried to the sight of the Forms – in terms of the Phaedran Palinode – Polemarchus proved to be dishonest, as Plato saw it. He could not forgive him. Polemarchus was a metic, a resident alien in Athens; in Republic VIII Plato points to ‘the metic becoming equal with the citizen and the citizen with metic (metoikon de astȏi kai aston metoikȏi exisousthai)’ as almost the last stage of deterioration of democracy into tyranny (562e0-563a1, tr. Jowett), and in the Laws he stipulates that when a resident alien acquires property that exceeds the property of the third class citizens, he must take his property and leave the city within thirty days, and if he overstays, he must be executed and his property confiscated (915b-c). Polemarchus was executed by the Athenian aristocrats under the rule of the Thirty, and his property was confiscated.
Socrates closes his discussion with Polemarchus on justice with the words: ‘Do you know (All oistha) whose saying I believe it to be (hou moi dokei einai to rȇma), the saying (to phanai) that justice is benefiting friends (dikaion einai tous men philous ȏphelein) and harming enemies (tous d’ echthrous blaptein)?’ – Polemarchus: ‘Whose (Tinos;)?’ – Soc. ‘I believe it to be the saying of Periander (Oimai auto Periandrou) or Perdiccas (ȇ Perdikkou) or Xerxes (ȇ Xerxou) or Ismenias the Theban (ȇ Ismȇniou tou Thȇbaiou) or of some other rich man who had a great opinion of his own power (ȇ tinos allou mega oiomenou dunasthai plousiou andros, 336a1-7).’
Adam notes ad loc.: ‘Periander, Xerxes and Perdiccas are taken as types of tyrants … The expedition of Xerxes against Greece is cited by Callicles in Gorgias 483 D in connection with the doctrine that might is right … Ismenias is mentioned again in Meno 90 A as having become rich … There can be no doubt that he is to be identified with the Ismenias who in 395 took money from Timocrates the Rhodian, envoy of the Persian King, in order to stir up war against Sparta.’