The Inferno: Theme Analysis

Separation from God Leads to Unhappiness
Dante himself said that the purpose of his Divine Comedy as a whole was to free living human beings from misery and to take them to the state of happiness. The Inferno contributes to that purpose in many ways, but perhaps most importantly by the way it embodies the theme that separation from and rejection of the divine "love that moves the sun and the other stars" leads inevitably to unhappiness, and the more deliberately one chooses to harm oneself and others in an attempt to get happiness by centering on the ego instead of on divine love, the farther one actually moves away from life and love and everything that brings real happiness. Moreover, this ego-centeredness rots and corrupts society as well as the individual.
The whole structure of Hell embodies this theme. Hell is a vast pit that reaches from the surface of the earth to its center, and at each level the pit is narrower and darker. The farther down Dante and Virgil go, the stronger grows the sense of claustrophobia, of being trapped in stench and noise and torment, until at the bottom of Hell we find ice-almost total absence of life. Those who simply gave way to lust, gluttony, avarice, and anger occupy the highest levels. Then come those who deliberately chose to do violence to themselves and others in pursuit of their ends. Finally come those who deliberately misuse what is most distinctively human-the power to think, to speak, to reveal one's truth to another human being. To be truly human is to be guided by the natural bond of love that unites all human beings, and to honor the special bonds of love created by kinship and shared nationality, or the yet more sacred bonds entered into voluntarily by inviting someone as a guest or by swearing allegiance to someone. Those at the lowest levels have hardened themselves so completely that they have violated those bonds; they are scarcely human.
The way the souls relate to each other embodies this theme. In the Second Circle, Paolo and Francesca seem to be joined together in misery. After that, no soul in Hell shows any concern for any other, and indeed they begin to show hostility toward each other and then to try to make each other's sufferings worse. In the ice at the bottom of the pit of Hell that so perfectly symbolizes the paralysis of all real life and feeling, we meet Ugolino and Ruggieri, joined by hatred for eternity, as the one gnaws on the other. The effect of such images is heightened by the contrast between the way the damned treat each other and the way Virgil and Dante interact, with Virgil always the kind father, Dante the grateful, affectionate son.
The way Dante portrays Satan makes the theme even more obvious, especially when his Satan is contrasted with other images of Satan. The Satan of Milton's Paradise Lost, for example, still has some of the power and beauty he had when he was the most powerful and beautiful of all the angels. He is active, able in Hell to make powerful speeches, and able to leave Hell to tempt Eve. His rhetoric has even convinced some later readers that there is something noble about his decision to rebel against God: "Better to reign in Hell than serve in Heaven," he says. Dante's Satan is ugly and impotent, completely trapped in the ice created by the flapping of his own wings, and nothing about him could appeal to even the most rebellious adolescent. The theme, "This is not what you really want," could not be more powerfully expressed.
Even a Flawed Human Being Can Face Hell and Learn from the Experience
Another important way Dante chooses to accomplish his purpose is to embody the theme that even a fearful and deeply flawed human being can face the horrors of Hell (allegorically, all the darkness in one's own soul) and learn and grow from the experience, simply by wanting to grow and by being willing to accept the help that is necessary-and that will be forthcoming. He embodies this theme, first by making himself the "hero" of his own poem, and then by the way he portrays himself at this stage in his life-that is, by the way he portrays Dante the pilgrim. Dante the pilgrim has good intentions-once he finds himself again and realizes that he is lost in the Dark Wood, he is horrified and wants to escape. When he sees the sun on the mountain, he starts moving toward it right away. But when beasts come against him, instead of slaying them as the hero of a classical epic might, he is helplessly driven back into the Dark Wood. Only Virgil can save him, and his chief merit is that he is able to appreciate Virgil and willing to follow him.
But even that merit is limited. The first canto ends with Dante following Virgil; the second canto begins with Dante having second thoughts. He is no classical hero, like Aeneas, the hero of Virgil's Aeneid, who went down into the Underworld and returned. He is no saint, like Paul, who traveled up into Heaven. Nobody would ever dream that he was worthy to go on an adventure like this, and neither would he. In the same way, all through the Inferno, again and again, Dante is terrified and even ready to go back, but Virgil's encouragement and help make it possible for him to "feel the fear and do it anyway." So Dante the author brings his readers close to his unheroic hero, and encourages us all to see this journey as one that perhaps even we could undertake.
Human Wisdom Is Never Enough
Another important theme of the Inferno is that, though human wisdom is essential to moving from a state of misery to one of happiness, human wisdom is never enough. One must ultimately rely on divine love and grace. Thus in the second canto we learn that Virgil, the embodiment of the highest human wisdom, has only come to Dante's aid because he has been summoned by Beatrice, who was for Dante, even when he was a young man, a revelation of divine love so powerful that he portrayed her as a Christ figure in his early work, La Vita Nuova (The New Life). And it was the Virgin Mary, understood by the Catholic Church as the mother of God and chosen by God to be the purveyor of divine grace to human beings, who first saw Dante's plight and started the process of bringing him help. It is the knowledge that divine love and grace are at work that enables the fearful Dante to take heart and move on into Hell. And Virgil on his own could never have brought Dante through; he was helpless to open the gates of the City of Dis. An angel comes to their aid and opens them effortlessly. And Virgil told Dante in the very beginning that once Dante was ready to rise into Heaven, someone else (and that someone else is of course Beatrice) will have to take over.