The role of purgatory in the Comedy also illustrates Dante’s affirmative presupposition regarding nature and grace. The deceased Christian does not die and go straight to heaven. This “Protestant” understanding would entail that the sinner instantly becomes a saint. This is an example of grace replacing nature. Dante’s theology of positive theology would not allow this. The sinner cannot immediately conform to God. Rather, the natural soul must be perfect by grace. The soul, with the help of grace, must ascend the mountain and thereby become perfect. The former life and its sins are not eradicated. Transformation is real. It is a step-by-step “positive” way.
Dante’s Purgatorio also provides insight as to how natural virtue opens the way for supernatural virtue. The poet praises the ancients as “men who with their reason probed the depths…thereby bequeathing ethics to the world.” (Purg 18.67-69) The positive role of reason, philosophy and natural virtue is alluded to in the Christological procession where four ladies dressed in purple robes dance on the “left wheel” of Christ’s chariot and three ladies dressed in red, green, and white, dance on the “right wheel” of Christ’s chariot. (Purg. 32.120-132) Dante shows the balance of the Cardinal Virtues of Prudence, Justice, Fortitude, and Temperance (dressed in purple) with the Theological Virtues of Faith, Hope, and Charity (dressed in white, green, and red, respectively). The formal virtues are natural and the latter are supernatural—yet it seems that they together steer the chariot of Christ.