This opening canto is an introduction to the entire Divine Comedy. This is made clear in the closing lines, when Virgil tells Dante that he can guide him only so far towards Paradise, and then another guide will have to take over because Virgil, being born before the birth of Jesus Christ, cannot ever be admitted to the "Blessed Realms."
The opening lines suggest first a realistic journey through a strange and eerie place, but after the first tercet (three lines), it is apparent that everything will be in terms of an allegory. It is a story of Dante's journey through life to salvation.
It begins when Dante is halfway through his life — 35 years old, half of the biblical three score and ten — and he has lost his way. When Dante speaks of having strayed from the right path, the reader should not assume that Dante has committed any specific sin or crime. Throughout the poem, Dante is advocating a strict adherence to medieval Catholic theology: Man must consciously strive for righteousness and morality. In its simplest terms, Man can often become so involved with the day-to-day affairs of simply living that he will gradually relapse into a sort of lethargy in which he strays from the very strict paths of morality.
