The Myth of Er closes Plato’s Republic: the soldier Er dies in battle, revives on his funeral pyre twelve days later, and reports what he witnessed of the soul’s journey between lives. The dead are judged, rewarded or purified, and then gathered to choose their next lives from a scattering of possible lots - tyrants and animals, poets and rulers. Crucially, the choice is free but made with whatever Wisdom the soul has cultivated: those who lived by habit rather than philosophy often grab glittering lives that conceal ruin, while Odysseus, cured of ambition, searches long for the quiet life of a private man and calls it the best choice of all.
After choosing, each soul is assigned a daimon - a guardian spirit that accompanies it through life as the keeper of its chosen pattern. The souls then pass beneath the throne of Necessity, whose daughters the Fates seal the lots, and cross the plain of Lethe, where all but the disciplined drink deep of the waters of forgetfulness. Birth thus erases the memory of the choice - which is why the life we find ourselves living can feel simultaneously alien and strangely ours. Plato’s anamnesis - knowledge as recollection - is the partial undoing of that drink: philosophy as remembering what the soul already knows.
The myth carries the Republic’s ethical payload: responsibility lies with the chooser, not with God (“the blame is his who chooses”), and the practice of Virtue and orientation toward the Good matter precisely because they determine how wisely we choose - in the myth’s frame, for the next life; read psychologically, in every present moment. Its cosmology of ascent, descent, and return prefigures the Neoplatonic doctrine of Emanation & Descent, and its cycle of lives parallels Eastern accounts of samsara and karma, with the distinctive Greek emphasis on choice at the threshold.
James Hillman’s acorn theory revives the myth as depth psychology: the daimon becomes the innate image of character and calling, and the forgotten choice becomes the sense that one’s life carries a pattern one did not consciously author. Understanding the Myth of Er means reading it as Plato intended myth to work - not literal doctrine but a vehicle for truths about soul, freedom, and destiny that argument alone cannot carry.
See also daimon, soul, anamnesis, Virtue, the Good, acorn theory, reincarnation, Emanation & Descent