Paradise Canto VII: (Second Heaven, Sphere of Mercury)
Having finished his story, Justinian and his friends start singing a Latin hymn, during which they dance and spin away.
Dante still has questions about Justinian's story.
Beatrice reads his and smiles knowingly. She paraphrases Dante's question for us. If Christ's crucifixion was just, in that it redeemed man for his original sin, how could it be just for God to then take vengeance on the Jews for taking part in it? Good question.
So Beatrice lays out the truth: since Adam gave into temptation, he plunged all of mankind into sin. Nobody could go to Heaven until the coming of Christ. Christ's Incarnation ensured that he was both man and God simultaneously. Both natures were in him united but also distinct. It's one of those miracles that we humans can't really understand. Christ's human nature was pure—because he was united with God—but in itself, human nature was sinful because of Adam's mistake. So, paradoxically the Crucifixion was both just, because it punished Christ's human half, and unjust, because it offended Christ's divine half.
God was pleased because man had redeemed himself and could be allowed into Heaven once more. According to Beatrice, the Jews were pleased they had killed the Christians' Savior. But God was also upset at the Jews for killing His son. So this explanation should satisfy Dante as to why God's actions after the Crucifixion were just.
Now Beatrice anticipates Dante's next question: why did man need to be redeemed in exactly this way? Why did Christ have to die?
Beatrice explains, but first warns Dante that nobody can fully understand God. Everything that derives directly from God is immortal, because it has His goodness and cannot be influenced by anything else. Such a creature is most like God. Mankind was once this lucky—both immortal and free—but then Adam sinned. And because of that one error, man showed himself unworthy of both his immortality and his freedom.
Man needed to atone for this sin and he could only gain back his freedom or immortality if God were to forgive everyone or if man were to offer some sort of compensation to God. Here's the catch, though: Adam's sin was believing what the serpent said—that once he ate of the fruit, he would be like God. So Adam's sin was one of pride, thinking he could be as high and mighty as God. Nothing man could do would make up for so great a sin. God, then, was forced to forgive man out of mercy.
God was merciful in giving Himself—in the form of Christ—to pay penance for man's sins. And He was also just because the human part of Christ suffered for Adam's sin.
Beatrice returns to one point, that all things coming from God are immortal. She reads Dante's mind and asks his question for him—so why aren't things like fire, water, air, and earth everlasting too? The answer: only the angels, Heaven itself, and man were directly created by God. Everything else was created by "created powers" (called the Angelic Intelligences), which aren't immortal.
Remember, she says, that God directly created both the human soul (with His breath) and the human body (by shaping Adam), so both parts of man are immortal. This implies that the death of the human body must be followed by its resurrection.