The second canticle opens with one of the most celebrated invocations in the entire Comedy: Dante calls upon the Muses, and in particular Calliope, goddess of epic poetry, to aid him in singing of a realm he has never before treated. The metaphor is nautical — his genius is a vessel that must sail better waters than the cruel sea of Hell he has just crossed. The emotional register shifts immediately: the oppressive dark of the Inferno gives way to a trembling sweetness of sapphire sky, the orient just beginning to pearl before the dawn.
Four stars never seen except by the first humans in Eden blaze in the southern sky — an allegory of the four cardinal virtues (Prudence, Justice, Fortitude, Temperance) that Purgatory exists to restore. The two poets have arrived at the base of Mount Purgatory, an island in the southern hemisphere directly antipodal to Jerusalem. Dante's face still bears the grime of Hell.
A stern old man appears — Cato of Utica, the Roman Stoic who chose suicide over surrender to Caesar, whose death made him the symbol of freedom and moral rectitude for the ancient world. His sudden appearance is surprising: historically, Cato was a pagan and a suicide. Dante's choice of him as Purgatory's warden is a bold theological provocation, suggesting that a kind of natural virtue, fully committed, may merit proximity to salvation, if not salvation itself. Virgil explains their journey and invokes the name of Cato's dead wife Marcia — Cato sharply dismisses sentiment. They may proceed.
Virgil is directed to wash Dante's face clean of the smoke and tears of Hell with the dew from the nearby grass, and to gird Dante with a humble reed plucked from the shore. When Virgil bends to gather the reed, another springs up immediately in its place — a first quiet miracle signaling that Purgatory, unlike Hell, is a realm of regeneration and growth.