•Why it earns a slot
The Symposium is the foundational text in Western philosophy for the idea that erotic desire, properly redirected, can ascend to the contemplation of eternal truth, and Diotima's ladder remains one of the most influential arguments in the history of metaphysics and aesthetics.
At a dinner party celebrating the playwright Agathon's tragic victory, a series of guests take turns delivering speeches in praise of the god Love. The speeches range from mythological and rhetorical to philosophical, culminating in Socrates' account of a ladder of ascent from physical beauty to the eternal Form of Beauty itself, as taught to him by the wise woman Diotima. The evening ends with the drunken Alcibiades arriving to deliver an unplanned tribute to Socrates himself, praising his uncanny wisdom and iron self-mastery.
This distillation is written from the freely available original, which is always the better read when you have the time: gutenberg.org.