The smoke clears and Dante has three final visions of wrath punished: Procne transformed to a swallow for murdering her son; Haman crucified (in his pride and rage he had plotted genocide against the Jews and was hanged on the very gallows he built for Mordecai); and Amata, wife of King Latinus, who in wrath and grief hanged herself. These come in rapid succession like dreams at the edge of sleep — violent, condensed, emblematic.
An angel appears, so radiant that Dante must look away. He erases another P and points them upward. On the staircase between the third and fourth terraces, night falls. They sit. And here Virgil delivers the single most important expository passage of Purgatorio: the comprehensive theory of love on which the entire moral architecture of the mountain rests. All human action, he explains, is motivated by love. Love can err in three ways: by loving what should not be loved (the sins of the upper three terraces: pride, envy, wrath, all involve loving one's own excellence or possession at the expense of others); by loving good things too little (sloth on the fourth terrace); or by loving good things too much (avarice, gluttony, lust on the upper three terraces). Love is thus the root of virtue and vice alike. The correction is not to kill desire but to order it rightly.