In the Parmenides Plato endows some of the most telling arguments against the Forms with the authority of Parmenides. Without offering any counterarguments Parmenides avers that only to ‘a man of considerable natural gifts’ (andros panu men euphuous, 135a7), ‘willing to follow a man who is showing him the Forms in course of a prolonged study, starting from afar’ (etheloi de panu polla kai porrȏthen pragmateuomenou tou endeiknumenou hepesthai, 133b9-c1), it can be shown that the arguments against the Forms are false (echoi tis endeixasthai hoti pseudetai, 133b6-7). These words on their own point to the Republic, but Plato makes it double sure that the reader gets the point; the Parmenides opens with the words: ‘When we arrived at Athens, we met Adeimantus and Glaucon in the Agora’; these two bothers of Plato are Socrates’ main interlocutors in the Republic.
I have argued that Plato wrote the Parmenides after returning from Sicily in 366 B.C., following his unsuccessful, yet open-ended attempt to transform the Syracusan tyrant Dionysius the Younger into a philosopher-ruler; Plato agreed to return to Syracuse in order to resume his instruction of Dionysius, prepared to devote the rest of his life to the task of educating him. The Parmenides, hand in hand with the Republic, was to protect his disciples from the attacks against the Forms, such as Parmenides proffers in the dialogue, after his departure.
Presumably, Plato’s departure from Sicily was to be short; Dionysius wanted to end the war in which he had been engaged and call Plato back as soon as he made his own power more secure (Seventh Letter 338a). But as the time passed by and Plato’s stay in Athens proved to be longer than expected, Plato had time to do more. The road to the Forms outlined in the Republic begins too far from the beginning of the dialogue, in the fifth book. And so Plato wrote the Symposium – in which he outlines a life-long ascent to the Form of Beauty in a compressed way in Socrates’ speech on love – linking it to the Parmenides by the figure of Glaucon.
The Symposium is not designed to replace the arduous study leading to the Forms in the Republic, but to supplement it. In the preamble to the Symposium we learn that Apollodorus had narrated to Glaucon the speeches on love that he is going to narrate in the dialogue, and that he told him on that occasion: ‘There was a time when I was running about the world, fancying myself to be well employed, but I was really a most wretched being, no better than you are now. I thought that I ought to do anything rather than be a philosopher.’ (173a1-3, tr. Jowett) This remark points to Glaucon’s response to Socrates’ pronouncement in Republic V that ‘until philosophers are kings in their cities, or the kings and princes of this world have the spirit and power of philosophy, cities will never have rest from their evils’ (473c11-d6, tr. Jowett): ‘Socrates, what do you mean? I would have you consider that the word which you have uttered is one at which numerous persons, and very respectable persons too, in a figure pulling off their coats all in a moment and seizing any weapon that comes to hand, will run at you might and main before you know where you are, intending to do heaven knows what; and if you don’t prepare an answer and make good your escape, you will be “pared by their fine wits, and no mistake.’ – Socrates: ‘You got me into the scrape.’ – Glaucon: ‘And I was quite right; however, I will do what I can to protect you; but I can only give you goodwill and encouragement (parakeleuesthai, Jowett’s ‘good advice’ is out of place), and, perhaps, I may be able to fit answers to your questions better than another – that is all. And now, having such an auxiliary, you must do your best to show the unbelievers that you are right.’ (173e6-174b2, tr. Jowett)
Socrates begins by defining philosophers as ‘lovers of the vision of truth’ (tous tȇs alȇtheias philotheamonas). – Glaucon: ‘I should like to know what you mean (alla pȏs auto legeis)?’ – Socrates: ‘To another I might have a difficulty in explaining (Oudamȏs raidiȏs pros ge allon); but I am sure that you will admit a proposition which I am about to make (se de oimai homologȇsein moi to toionde).’ – Glaucon: ‘What is the proposition’ (To poion)?’ – Socrates: ‘That since beauty is the opposition of ugliness (Epeidȇ estin enantion kalon aischrȏi), they are two (duo autȏi einai)?’ – Glaucon: ‘Certainly’ (Pȏs d’ou). – Socrates: ‘And inasmuch they are two, each of them is one’ (Oukoun epeidȇ duo, kai hen hekateron). – Glaucon: ‘True again’ (Kai touto). – Socrates: ‘And of just (Kai peri dȇ dikaiou) and unjust (kai adikou), good (kai agathou) and evil (kai kakou), and of every other form (kai pantȏn tȏn eidȏn peri), the same remark holds (ho autos logos): taken singly, each of them is one (auto men hen hekaston einai); but from the various combinations of them with actions and bodies and with one another (tȇi de tȏn praxeȏn kai sȏmatȏn kai allȇlȏn koinȏniai), they are seen in all sorts of lights and appear many (pantachou phantazomena polla phainesthai hekaston)?’ – Glaucon: ‘Very true’ (Orthȏs legeis). (475e4-476a8, tr. Jowett)
And so Socrates takes Glaucon, Adeimantus, and the rest of the audience on the road that culminates in the sixth book of the Republic with a glimpse of the Form of the Good (505a-b).