Notes

172b, Phoenix, son of Philip

According to Fowler, nothing is known of this man. 

172c, Glaucon

According to Fowler, this is probably Plato's brother, who plays a prominent role in the Republic (e.g. 368a) as a devotee of Socrates. The implication is that Glaucon is inspired by Apollodorus' account of the symposium to start following Socrates, and this is one of the prominent stories that he told his brother Plato. In the Republic, Plato presents Glaucon as the person who best understood both the grand scope, and the minute details of Socrates' philosophy. I interpret the oral transmission of the dialogues as significantly coming to Plato through Glaucon. 

173e, raving mad and staggering about

The Dionysian theme of the dialogue is foreshadowed here. 

Goodman’s

The name Agathon resembles the Greek for good men’s in the proverb, which seems to have been: αὐτόματοι δ’ ἀγαθοὶ ἀγαθῶν ἐπὶ δαῖτας ἴασι (Athen. i. 8A; Bacchyl. fr. 33). The corruption consists in putting the dative Ἀγάθων(ἰ) for ἀγαθῶν; though perhaps the reference is to another form of the proverb which had δειλῶν (cravens’) instead of ἀγαθῶν [Fowler].

Homer

Hom. Il. 17.587 Μενέλαον ὑπετρέσας, ὃ τὸ πάρος γε μαλθακὸς αἰχμητής, and Hom. Il. 2.408 αὐτόματος δέ οἱ ἦλθε βοὴν ἀγαθὸς Μενέλαος [Fowler].

173d, GLAUCON

I've replaced "COMPANION" from the Stephanus text with "GLAUCON." Compare note to 172c above. Because of Glaucon's antagonism to Apollodorus, I suspect that scribes have obscured Glaucon's identity. My feeling is that the character of Glaucon is enriched by seeing him here just as he is, being drawn toward the Socratic ethos and lifestyle. 

174c, a spearman soft

Compare Apollodorus' moniker of the "Soft" (173d). 

174d, If two go along together, there’s one before another

Compare Homer, Iliad 10.224 σύν τε δύ’ ἐρχομένω, καί τε πρὸ ὃ τοῦ ἐνόησεν ὅππως κέρδος ἔηι, if two go along together, there’s one to espy before another how a profit may be had.

175b, a habit he has

Compare Phaedo, 67c and following. 

175b, a method I have never tried before

According to Fowler, this clause is probably an asideto his guests.

176a, the god

Agathon is celebrating his winning of the prize for drama the previous day as part of the weeks-long Dionysian festival. "The god" here is the god of the festival. 

177a, not mine the tale

Fowler: Eurip. fr. 488 οὐκ ἐμὸς ὁ μῦθος, ἀλλ’ ἐμῆς μητρὸς ἐμῆς μητρὸς πάρα, not mine the tale; my mother taught it me.

177b, Prodicus

The moralizing sophist, famous for his parable of The Choice of Heracles (Xen. Mem. 2.1.21), where the appeal of Virtue prevails over that of Vice.

178a, so too the whole of what he told me is beyond mine

Note the layers of transmission. Apollodorus is telling a story, which he heard from Aristodemus, to Glaucon, who would later tell it to Plato, who would then at some later time after that write it down, and revise it for publication. I imagine Plato asking Glaucon to tell certain stories over and over again—and this being one that he mulled over for quite a long time. 

178b, parents of Eros there are none

Socrates will later dispute this. 

178b, and thereafter rose/ Broad-breasted Earth, sure seat of all for aye,/ And Eros

Fowler: Hes. Theog. 116

178b, Acusilaus

Fowler: An Argive compiler of genealogies in the first part of the fifth century B.C.

178b invented Eros before all other gods

Fowler: Parmenides fr. 132; Cf. Aristot. Met. 1.984b.

178e a little band victorious over all the world

Fowler: There was such a sacred band (ἱερὸς λόχος) at Thebes, which distinguished itself at Leuctra (371 B.C.).

179b, fury inspired

Fowler: Hom. Il. 10.482; Hom. Il. 15.262

179b, Alcestis

Alcestis willingly died in stead of her husband, and when she arrived in the underworld, Persephone, so moved by Alcestis' love for her husband, allowed her to return to life. For further details, see Joshua J. Mark, "Alcestis," in World History Encyclopedia. 

The original source is very brief. 

179e Isles of the Blessed

Fowler: Pindar O. 2.78ff. (Hom. Od. 11.467ff., places him in Hades).

179e he would die as surely as he slew Hector

Fowler: Hom. Il. 18.96.

180a, nonsense when he says that Achilles desired Patroclus

Fowler: Aesch. Myrm. fr. 135-136.

180a as Homer says

Fowler: Hom. Il. 11.786. 

180b when the beloved cherishes the lover

"Cherishes" translating ἀγαπᾷ (agape), which is more of a familial love, than ἐράω (eraoo, congate of eros), which is translated as erotic "love" elsewhere. 

180d whence we name her "heavenly"

Fowler: Hdt. 1.105, Hdt. 1.131; Paus. 1.14.7.

180d, her we call "common"

Fowler: Paus. 1.22.3.

193c, as if I speak of Pausanias and Agathon

Aristophanes indicates here that Pausanias and Agathon are in some sort of homosexual relationship. 

198a, young man's

Agathon is the younger man in the relationship with Pausanias (compare 193c). 

198c, Gorgias' "terrifying head"

Compare Hom. Od. 11.632. 

201a, Eros [Ἔρως] must be the love [ἔρως] of beauty [κάλλους], not shame [αἴσχους]?

Socrates is taking Agathon's approach a step further—shifting focus to beauty, the desired object of Eros. And Socrates is also bringing in especially what Pausanias had to say about shame. 

201d, Diotima [Διοτίμας], a Mantinean [Μαντινικῆς] woman

Diotima is a woman from Mantineia. [The name "Mantineia" [Μαντίνεια] suggests a root in mantis [μάντις], "prophet." "Diotima" also suggests priestly and prophetic things—Dio [Διός (Zeus)] + time [τιμή (honor)]—meaning "Honored by Zeus," or "Honoring Zeus." 

204b, Wisdom being among the most beautiful things

Wisdom is among the most beautiful things, but it is not beauty itself—the absolutely most beautiful thing. 

211a, that which, first, is always really existing—neither coming to be, nor being destroyed, etc. 

Compare Xenophanes of Kolophon, especially fragments 1 - 7 (as numbered by Fairbanks) and the testimony of Clement of Alexandria (on page 78 of Fairbanks). There is some similarity between Diotima's notion of "beauty itself" and Xenophanes' monotheistic god. Comparing further with Anselm's Proslogium, we see that the pure idea of beauty is certainly perfectly good, and arguably eternal—but is neither omniscient, nor omnipotent. In regard to omnipotence, note that it is the power of Eros that drives the philosopher toward absolute beauty. 

211b, it is always really existing as a single perceptible form

Compare Plato, Sophist, 242d-e and Aristotle, Metaphysics, 1.5, 986b. Although Diotima argues that beauty itself is an unchanging unity, it is not the unity of all beautiful things (much less of all things in general). Rather, as an idea, the beautiful has a separate and distinct existence from the sensory beautiful objects that partake in it. 

223c, for the nights were long

This is the strongest evidence internal to the Symposium that the party takes place following the Lenaia festival of January/February—not the City Dionysia of March/April.