n. The concept that the punishment of an individual's soul in Hell corresponds to the sin that person committed on earth.
Contrapasso (or, in modern Italian, contrappasso), from the Latin contra and patior, "suffer the opposite": refers to the punishment of souls in Dante's Inferno, "by a process either resembling or contrasting with the sin itself." A similar process, though a penitential one, occurs in the Purgatorio.
One of many examples of contrapasso occurs in the 4th Bolgia of the 8th circle of Hell (Inferno, Canto XX), where the sorcerers, astrologers, and false prophets have their heads twisted around on their bodies backward, so that they "found it necessary to walk backward, / because they could not see ahead of them." While referring primarily to attempts to see into the future by forbidden means, this also symbolises the twisted nature of magic in general. Such a contrapasso "functions not merely as a form of divine revenge, but rather as the fulfilment of a destiny freely chosen by each soul during his or her life."
The word contrapasso can be found in Canto XXVIII of the Inferno, in which the decapitated Bertran de Born declares: "Così s'osserva in me lo contrapasso" (XXVIII, 142) which Longfellow translates: "Thus is observed in me the counterpoise" De Born is in the 9th Bolgia of schismatics, for (Dante believes) causing the rebellion of Henry the Young King against his father, Henry II of England. He is decapitated there as a contrapasso for his (supposed) act of political decapitation in undermining a rightful head of state.
Dante inherited the idea and the name of contrapasso from theological ( Thomas Aquinas's Summa Theologica) and literary (Medieval "visions", such as Visio Pauli, Visio Alberici, and Visio Tungdali) sources.