Dream of Witch / Siren: Terrace 4, Purgatorio 19   Dante's second dream, perhaps even more strongly than most dreams, encourages a psychoanalytical interpretation. He first sees a woman who is deformed (twisted feet, crippled hands), cross-eyed, sallow, and babbling; Dante's gaze then transforms her into a vision of loveliness with a beautiful singing voice. Identifying herself as the siren who bewitches sailors, she boasts of having diverted Ulysses from his voyage (19.19-24). At this point another woman, holy in appearance, forcefully intervenes by calling to account Virgil, who immediately rips open the siren's dress, thus revealing a belly that emits a noxious odor.   It is common in medieval literature to represent the internal conflicts within an individual's psyche or conscience as an external battle of spirits, a genre known as psychomachia that Dante himself uses to great effect in his earlier work, the autobiographical Vita Nuova. The external actors in Dante's dreams also constitute the psyche in Freudian terms: the siren / witch as the object of Dante's unconscious desire (id), the holy woman as the restraining authority (superego), and Virgil as the "managing" ego. Consistent with the dream's emphasis on desire and false appearances, Virgil maps this "ancient witch" onto the sins of the next three terraces (17.58-60), all characterized by excessive desire for lesser, secondary goods (18.133-9).