In the myths at the end of the Phaedo, Republic, and Gorgias, Socrates seems to suggest that certain souls are so wicked that they cannot be cured, even in the afterlife. A passage from the Gorgias provides a chilling illustration: "From among those who have committed the ultimate wrongs and who because of such crimes have become incurable come the ones who are made examples of" (525c). These suffer "for all time the most grievous, intensely painful and frightening sufferings for their errors" (525c).
Most contemporary scholarsthink that Socrates — and by extension Plato — really believed that certain extremely unjust souls are incurable. At any rate, they maintain this about the Plato who wrote the Gorgias, Republic, and Phaedo myths. Some (e.g. Kamtekar 2016) suggest that in later works like the Timaeus and Laws, the notion that souls can be incurable is dropped. But an older interpretive tradition stands opposed to today's consensus. The Neoplatonists tended to find the notion of a perpetually incurable soul disturbing, unnatural, and un-Platonic. Olympiodorus,in his commentary on the Gorgias, even goes so far as to claim that it would be better to affirm the mortality of the soul than to claim that there is never-ending punishment in the afterlife for incurables. The Neoplatonists who rejected incurability maintained that, when Socrates seems to allege the incurability of certain souls, he is either (a) speaking politically useful falsehoods, or (b) indicating only that certain souls cannot be cured for a very great (but finite!) span of time, an aeon.
My talk consists of two parts. In the first part, I offer a new defense of the idea that Plato never believed that a soul could be incurable — the stories told in Phaedrus and Timaeus agree with the myths in the Phaedo, Republic, and Gorgias. While many Neoplatonists opted for the "aeon of finite duration" line of defense, I find this view insufficiently borne out by the texts. Instead, I will suggest that the myths that speak of incurable souls — while they also contain much truth — exaggerate the extent to which a soul can become corrupt for the sake of turning certain of Socrates's less philosophical listeners away from vice. Moreover, Plato includes within the framing and details of these myths indications to the perceptive reader that the surface-level reading of each myth cannot be entirely trusted.
Let me offer a little bit of evidence by working through how my view handles one example. The Myth of Er that ends the Republic might seem to suggest that Socrates endorses the notion that certain extremely wicked people, many of them tyrants, are incurable and will receive everlasting torment. I argue that the opposite is the myth's deeper message — no one is incurable, and in fact everyone will be cured.
According to Socrates, the Myth of Er is"not an Alcinous story" (614b). On one level this is simply a reference to Odysseus's journey to the underworld in the Odyssey, which Odysseus narrates to King Alcinous. But etymologically, "Alcinous" means roughly "Strong of Mind." Hence, Socrates is warning us that the brave warrior Er may be somewhat lacking when it comes to wits. Now, in the story, certain divine judges tell Er that he is supposed to thoroughly observe the underworld and report to humanity about what he sees (614c-d). Then Er overhears two men talking to one another; one claims to have witnessed "savage men, fiery to behold" (615e) tormenting certain particularly wicked evildoers and "indicating . . . that they were going to be tossed into Tartarus" (616a). The fiery men don't say that these prisoners are incurable, nor that they will never be granted another incarnation. These are inferences made by an anonymous man talking to another anonymous man, overheard and reported by one "not of strong mind" — or, at least, so Socrates tells his listeners, Thrasymachus among them. Plato's view, indeed!
Suppose I'm right: for Plato, all souls are always curable. So what? Why should that make me or anyone else feel any consolation or optimism? Isn't all this talk of souls and reincarnation just a bunch of hogwash, after all?
Well, maybe. I certainly used to think so. Endorsing reincarnation seemed to me like believing in ghosts or leprechauns. But after studying some cosmology (especially the "eternal inflation" theory) and reading Michael Huemer's 2021 paper "Existence Is Evidence of Immortality," I'm now much less sure. And I find it to be an idea of tremendous beauty, perhaps the only thought that gives me genuine consolation in the face of the "dark wind" of death blowing towards us all. "Certainly we shall rise, certainly we shall see and gladly, joyfully tell one another all that has been," in the immortal words of Alyosha Karamazov.
To me, this idea is most profound when combined with a notion of endless activity; Leibniz held that the greatest human happiness necessarily left room for "a perpetual progress to new pleasures and new perfections." Plato's myths give us a touchingly realistic portrait of this perpetual progress. We see it most clearly in the Myth of Er: no one (I claim) gets eternal punishment, but neither does any soul reach some static condition of eternal salvation. The most fortunate among us only glimpse the eternal Beings μόγις — scarcely and with difficulty. And then we forget, and make mistakes again, and suffer, but later on we're once again cured by our learning, and we taste unimaginable delights. Our deepest nature, as Plato stresses in many places, is that we're all souls that have seen all the true Beings, and thus virtue and friendship are our natural conditions. And somehow we're always in the middle of trying to return to that original wholeness, both within ourselves and in political communities. Our souls endlessly change and come back to themselves; we all just keep living, and we'll all see each other again.
 The translation is Zeyl's, from Cooper 1997.
 The treatment in Brickhouse & Smith 2002, for instance, is typical. It assumes that Socrates really thinks that certain souls are forever incurable, and it takes the critical question to be why he thinks so.
 Proclus, Damascius, and Syrianus, to list a few notable examples, also deny the incurability of the soul.
 50.2; compare also 24.5. Footnote 1004 on p.317 of Jackson, Lycos, & Tarrant (1998) contains an excellent brief summary of Neoplatonic reactions to the apparent doctrine of incurability.
 It is perhaps noteworthy that the gods do not employ the wisest of us humans in this task. Perhaps they do not want a messenger who would get to the bottom of matters like the case of the "incurables," preferring instead Er on the grounds that he will credulously report his impressions and the things he has heard as facts.
 Translations mine.
 A figure of course well known for always saying exactly what he thinks.
 Note also Socrates's postlude to the myth: he tells Glaucon that yes, the Myth of Er can save us if we are persuaded by it to live our lives with undefiled souls, but (ἀλλ᾽) that those persuaded by Socrates -- not the Myth -- will believe that the soul is "able to bear up against all goods and all evils" (ψυχὴν καὶ δυνατὴν πάντα μὲν κακὰ ἀνέχεσθαι, πάντα δὲ ἀγαθά, translation mine). The word I translate "bear up against," ἀνέχεσθαι, can also mean "to rise up." I take this to be a subtle hint that Er has misunderstood. No one suffers in Tartarus eternally. The soul always endures its sufferings and rises once more to the earth -- and perhaps even higher, to glimpse that upper realm full of eternal intelligible realities which we all beheld before our first birth.
 Translation from Pevear and Volokhonsky (2002).
 §18 of Principes de la nature et de la grace, fondés en raison, translation mine.
 Plato repeatedly uses this curious word when he talks about apprehension of the Forms, e.g. in Republic VII and in the chariot myth from the Phaedrus. Even the philosopher-kings, who are better prepared than any other people to gaze upon the Form of the Good, see it μόγις.