Why does Dante’s journey end with an immobilized sin (i.e., Satan held in place, powerless)?
Dante’s journey through hell begins with three animals attacking him at the base of the hill of Calvary. The leopard, lion, and she-wolf represent sin collectively (corresponding to different specific sins or categories of sin which are not in the scope of this question). After being attacked by sin, and consequently rescued by Virgil, Dante spends the rest of his journey directly witnessing the full effects of sin: namely eternal punishment in the Inferno. So what does it mean that Dante begins by facing mobile and active sin, but ends with a completely immobile and powerless sin, manifested in Lucifer’s position in hell?
If Inferno is treated as a completely separate book from the Divine Comedy, then it seems as though the change would be easy enough to explain away. If Dante travels through hell after being attacked by sin, he would recognize the path that sin would lead him to, and it would no longer have power over him. If Inferno is viewed in light of Purgatory and Paradise, the answer need not change significantly. Dante’s travels through hell bring him to the point where everyone he sees from now on will no longer be under the power of sin. Everyone in Purgatory is saved and everyone in Paradise is saved and done dealing with the effects of their personal sins.
The problem with both of these answers is that sin was still active on earth, and Lucifer is clearly portrayed as defeated and without power over even hell. If Jesus was right in saying that a kingdom divided will fall, then surely a kingdom without a leader will fall even faster. So the question really boils down to something like “Why does sin still have power at all, if Satan is immobilized?” The answer lies here: the Divine Comedy is a progression, detailing Dante’s experience as he moved through the earth, the bowels of hell, and on into the mountain of purgatory and into the heavens of paradise. It makes sense that by the time we reach the end of hell (and the beginning of purgatory) we could see Lucifer’s feet sticking up helplessly into the air.
So why does Dante end with immobilized sin? Dante does so because he realizes that for the true Christian, sin does not have a hold of us. Sin acts, but is a defeated kingdom. Lucifer may think he has power (and thus continues to flap his wings even in hell), but he truly is defeated.