In Aeschylus’ Prometheus Bound, the maiden Io describes, in violent terms, the sexual overtures of the god Zeus that are made to her in a dream. Her father, asking the oracle at Delphi for advice concerning these nightly visitations, is ordered by Apollo to drive his young daughter from her home to wander aimlessly over distant lands. Io describes how, attending her banishment, she is transformed into a heifer and driven mad. While the transformation into the heifer is directly attributed to Hera, Aeschylus leaves the origins and essential nature of Io’s madness vague. Compounded by contradictory accounts of her madness and its origins within the play itself, we are left with a patently mad young woman and yet with very little unambiguous reason for her madness. In order to resolve this ambiguity, I have chosen to make use of Lacanian psychoanalysis and its particular emphasis on the subject’s relationship with itself and with external reality. Focusing on Io’s account of her dream, I argue that her dream expresses her strong identification with an ego focused on childhood—an ego that is in the process of being undermined by her impending transition into adulthood. Ultimately, it is this state of contradiction, appearing in the figure of the Eye of Zeus, which reveals to Io the essential vanity of identification with both childhood and adulthood and which brings about her descent into madness.