Lino Pertile, an Italian linguist and Professor of Romance Languages and Literature at Harvard University, makes this astute observation in his introduction to Dante’s Inferno:
Being natural, the sins of incontinence offend God less, and therefore they are punished in the first four circles. In the second circle, the lustful are relentlessly buffeted by stormy winds; among them are Paolo and Francesca, the most famous couple of Dante’s Comedy. By virtue of their position at the start of Hell proper and its punishments, their sin acquires a founding value, so to speak. Just like the sin of Adam and Eve at the dawn of human history, the sin of Paolo and Francesca presents itself, at the beginning of Dante’s journey, as a catastrophe from which all other evils follow, even if not out of necessity. There is no good that love, unrestrained by reason, does not destroy; there is no evil to which such love does not lead. We begin by yielding to passion, and we end betraying and murdering Caesar and Christ: this is the story of humanity and the map of Dante’s Hell.
— The Cambridge Companion to Dante, edited by Rachel Jacoff