Eros (Platonic Love)

Plato's account of love, developed in the Symposium through Diotima's teaching (reported by Socrates). Its central original move is to redefine love away from the beautiful beloved (the object) toward the needy lover (the desirer): love is lack — "a thing that desires desires something of which it is in need" (200a) — so Love is neither beautiful nor good but a daimōn, an intermediate (metaxu) between mortal and immortal, ignorant and wise; he is the philosophos, who loves wisdom precisely because he lacks it. The real object of love is "possessing the good forever" — hence immortality, pursued by "giving birth in beauty" (tokos en kalōi), of body (children) or of soul (poems, laws, virtue). The teaching culminates in the ladder of love: an ascent from one beautiful body → all bodies → souls → laws and customs → knowledge → Beauty itself (auto to kalon), the Form that "always is and neither comes to be nor passes away" (211a). Platonic eros is thus acquisitive, ascending, and ultimately impersonal — the engine of the philosophical ascent, not an attachment to a particular.

Key Points

Love as lack (200a–201b): one desires only what one does not (yet) possess; even "I want to be healthy" reaches toward a future state. So Love lacks the beauty and good it pursues. (The Lysis already makes this move aporetically — "a thing desires what it is deficient in," 221d–e — so love-as-lack is a pre-Symposium deposit; see philia.)
The metaxu / daimōn (202d–204c): conceived by Poros (Resource) on Penia (Poverty), Love is "in between" — "always poor … a schemer after the beautiful." Like correct opinion (between knowledge and ignorance), Love occupies the productive middle.
The good, not beauty, is the end (204d–206a): "love is wanting to possess the good forever"; beauty is the medium of begetting, not the goal — "what Love wants is … reproduction and birth in beauty."
Immortality through reproduction (206b–209e): mortals secure "the good forever" only by leaving "something new" behind — bodily children, or the more deathless "children" of soul (Homer's poems, Lycurgus' laws).
The ladder (210a–211c): each rung is superseded, not merely added; the individual beloved is explicitly downgraded — "this wild gaping after just one body is a small thing … despise it" (210b).
Beauty itself (211a–b): the terminus, given in the canonical Form-formula ("itself by itself with itself … always one in form"), grasped "all of a sudden" (exaiphnēs) — the only Form Diotima names, and reached by erotic ascent, not recollection.

What the Concept Does

Converts desire into philosophy — by making love lack of the good/beautiful and the lover an intermediate, eros becomes the motive force of the ascent to the Forms; philosophia is a species of erōs.
Subordinates love to eudaimonism — love is reframed as a species of the universal desire for the good and for happiness ("every desire for good things … is the supreme … love," 205d), not an autonomous category of value.
Instrumentalizes the beautiful beloved — the particular's beauty becomes the occasion of the lover's self-perpetuation and ascent, a rung rather than an end.

What It Rejects

Love as union with a particular / restoration of a lost half — Diotima explicitly refutes Aristophanes' myth: "a lover does not seek the half or the whole, unless … it turns out to be good as well" (205e).
Love as possession of the beautiful — the beloved's beauty is the medium of begetting, not the thing wanted.
The irreplaceability of the beloved — the ascent requires treating love of "just one body" as "a small thing" to be transcended.

Stakes

Platonic eros is the philosophical defense of replaceability-as-ascent, and so the explicit ancestor-foil of every later love-of-the-irreplaceable. Against Simmel's "absolute love" — which makes the beloved's irreplaceability an a priori — Diotima's ladder makes the individual a replaceable step; Plato is the canonical defender of love-by-type. Against Nygren's *agape* (unmotivated, descending, creative), Diotima's acquisitive-ascending erōs is the paradigm Greek eros against which Christian love is defined. And the Symposium itself stages the counter-case: Alcibiades' praise of the irreplaceable, atopos Socrates is given the last word, and J.M.C. reads "Diotima is an invention" as Plato distancing himself from the ascent — so the tension between love-of-Form and love-of-individual is held open, not resolved.

Positions

Diotima / Socrates: love is lack, daimōn, desire for the good forever; the ascent transcends the particular toward Beauty itself.
Aristophanes (189a–193d): love is the longing for one's lost other half — restoration of an original wholeness; refuted by Diotima (205e).
Alcibiades (215a–222b): love of the singular, irreplaceable Socrates — the dialogue's staged protest against the ascent's impersonality. See claims#symposium-dramatizes-its-counter-thesis (candidate).

Connections

develops theory-of-forms — Beauty itself (211a–b) is a canonical Form-formula and a primary attestation; reached by erotic ascent (not recollection or division), and the sole Form thematized.
contrasts with individualism-of-love — replaceable rung vs. a priori irreplaceability; Plato as ancestor-foil of love-by-type. See claims#diotima-ascent-vs-individualism-of-love (candidate).
contrasts with negative-reality-of-love — both make love privation, but Diotima's lack is teleological (culminates in possessing Beauty), MP's/Proust's is constitutive and permanent.
contrasts with love-as-formative-category — Simmel makes love a fundamental autonomous axis; Diotima subordinates it to eudaimonist striving.
is the genealogical foil of christian-love — acquisitive-ascending erōs vs. descending agape.
contrasts with anamnesis — the Symposium ascends to the Forms via beauty as a ladder one climbs; the Phaedrus via beauty as what reminds — two distinct Platonic beauty-routes.
is the erotic-ascent route to to-kalon — the same to kalon the Hippias Major fails to define by elenchus, the Symposium reaches as "Beauty itself" by erotic ascent (211a–b): one object, two methods. See claims#plato-two-routes-to-the-kalon (live claim).
resolves the aporiai of philia — the Lysis poses love-as-lack, the neither-good-nor-bad intermediate lover, the regress-halting prōton philon, and the oikeion as unresolved puzzles; Diotima resolves them by subordinating love to the good (refuting the oikeion-as-other-half at 205e). See claims#plato-lysis-seeds-symposium-erotics (live claim).
contrasts with the Alcibiades I's true-lover — there (disputed) Socrates loves Alcibiades' soul, not his bloom, and so stays when the others leave (131c–132a): love of the irreplaceable particular, closer to the Symposium's Alcibiades counter-case than to Diotima's ascent that transcends the particular. The "Platonic love" etymon.

Open Questions

Does the ascent leave the beloved entirely behind, or return to love particulars better having seen Beauty itself? The text downgrades the particular but Alcibiades' speech keeps the question open.
Is the leap from "the great sea / science of beauty" to a separate eternal Beauty licensed by the erotic ascent, or imported in a mantic register Diotima disclaims (210e)?

Sources

plato-symposium — Diotima's teaching (201d–212a): love as lack (200a–201b), the metaxu (202d–204c), the good and immortality (204d–209e), the ladder (210a–211c), Beauty itself (211a–b); Alcibiades' counter-speech (215a–222b).
plato-alcibiades-1 — the true-lover frame: Socrates loves the soul (the self), not the body's bloom (131c–132a); love of the particular, the etymon of "Platonic love" (authorship disputed).