Seven virtues
The "Catechism of the Catholic Church" defines virtue as "a habitual and firm disposition to do the good." Traditionally, the seven Christian virtues or heavenly virtues combine the four classical cardinal virtues of prudence, justice, temperance and courage (or fortitude) with the three theological virtues of faith, hope and charity. These were adopted by the Church Fathers as the seven virtues.
T. K. Seung
Seung elucidates the poem's thematic unity by using three principles essential to medieval Christian thinking. The first principle is the medieval classification of virtues and sins. It provides the framework for understanding the formal structures of the three realms. Seung shows that Hell, Purgatory, and Paradise are structured in accordance with the medieval table of seven natural virtues and three supernatural virtues, which are implicitly celebrated in the ten spheres of Paradiso. The natural virtues are humility, mercy, meekness, fortitude, liberality, temperance, and chastity, and the supernatural virtues are the three theological virtues of faith, hope, and love. The contraries to the natural virtues are the seven deadly sins of pride, envy, wrath, sloth, avarice, gluttony, and lust, and they are condemned as sinful acts in the various sections of Inferno, and on the seven terraces of Purgatorio they appear as vicious dispositions being purged into their virtuous opposites. Moreover, in the beginning of Inferno the supernatural virtues are thematized as being absent; in the beginning of Purgatorio they appear as distorted; near the end of Purgatorio they are celebrated as regained; and finally in the last cantos of Paradiso they are presented in full display.