Dante is very clear that above all else, humans are defined by their ability to reason. Unlike all the other animals in creation, humans have the gift of rational thought and can distinguish between good and evil. Any individual person has the ability to engage in moral decision making.

This means, however, that humans are responsible for their actions. They are held accountable and sent to hell if their deeds in life violate God's law.

God's law dictates that humans use their reason to control their passions. This is why people who can't control their passions end up in hell. For example, the lovers Francesca and Paolo are ceaselessly buffeted and blown around by winds in hell because of their inability to exercise their reason and control their wild lust for one another.

Not controlling one's passions is a sin that is punished in hell, but far worse than that is using one's reason against God's will in a cold and calculating way. This can make the punishments in Dante's inferno seem "weird" or "wrong" to modern readers. For example, people who mass murder out of passion are punished harshly, but less severely than, say, embezzlers. This seems counter-intuitive until we remember that a crime against God's will that comes out of the emotions run amok, while bad, is less bad than a cold, calculating, planned violation of God's law. The person who deliberately plans to do the opposite of what God wants—the person who could have stepped back at any time and done the right thing—represents the worst abuse of human reason and thus deserves the worst punishment