A comparison between Book 3,21-25 of the Metamorphoses and Plato’s Republic 2,359c-360b is pivotal for understanding how Apuleius stages entry into the space of the fantastic. In both episodes, desire, sight and the forbidden collaborate in creating the passage to the world of fiction, shaping it as a dreamlike experience, a psychological event of the unconscious. But the similarity between Plato’s and Apuleius’ fiction can be illuminated especially through an examination of Plato’s monstrous images of the soul. The essay shows that for Plato and Apuleius the entrance to the fantastic is meant to shed light on the unfamiliar sides of the soul. Comparing the two episodes from the Republic and the Metamorphoses will allow us to see that they share a motivation: the staging of that unknown part of the soul that escapes the rule of the rational.