LitCharts assigns a color and icon to each theme in Purgatorio, which you can use to track the themes throughout the work.
Purgatory and the Heavenward Journey
Love, Sin, and God
Free Will
Spiritual Power vs. Earthly Power
Time
Summary
Analysis
The souls walking within the fire are puzzled by the fact that Dante is evidently alive. But before he can answer their curious questions, Dante is distracted by the sight of groups of souls pausing briefly to kiss one another. After they embrace, the groups of souls yell things like, “Sodom! Gomorrah!” and the story of Pasiphae, before dispersing in different directions—those guilty of homosexual lusts in one direction and those guilty of heterosexual lusts in another. After witnessing this, Dante chats with the souls of two poets who are known to him—Guido Guinizelli and Arnaut Daniel—before they both retreat back into the cleansing fire.
The point of the souls kissing is that the embraces are restrained—showing that the nature of the sin is its excess. Kept within appropriate boundaries (with the greater part of desire directed toward God, as always), the sexual desire is not itself considered to be intrinsically sinful. As examples of the sin of lust, the souls name the so-called sin of Sodom (the male residents of this Old Testament city engaged in sexual relations with male visitors) and the mythological Pasiphae, wife of the king of Crete, who lusted for a bull and subsequently became the mother of the Minotaur.