THE CITY OF DIS.--The gate of the city is defended by fiends, while the Furies appear upon the turrets, girt with greenest hydras and with serpents for hair, calling upon Medusa to come and turn Dante to stone. The Furies are symbols of hopeless remorse, and Medusa of the despair which renders repentance impossible. “A guilty deed is the death of the soul; but to despair is to go down into Hell” (St. Isidore, _cf._ Virgil’s words to Dante, _Inf._ ix. 55-57). Virgil can guard Dante from her, but he cannot open the gates; for the city of Dis is the mediaeval counterpart of the Virgilian Tartarus, through which the Sibyl could not lead Aeneas. With the sound of mighty tempest a messenger of Heaven passes the Styx with dry feet, and opens the portal with a little rod; he is a figure drawn from Mercury in the _Aeneid_ (iv.), but here transformed to an Angel, akin to those two terrible beings who summon the dead to rise in Luca Signorelli’s Last Judgment.[32] Within the gate, round the circuit of the walls and at the same level as the last circle, the sixth circle confines the Heretics and Epicureans in burning tombs. They seem to hold this intermediate position in accordance with the teaching of St. Thomas that Infidelity, if reduced to one of the capital sins, must be regarded as arising from Pride, but may come also from cupidity or some fleshly illusion; and, in a passage in the _Convivio_ (ii. 9), Dante appears to reduce one form of Heresy to _bestialitade_. Farinata degli Uberti, the Ghibelline hero of Montaperti, heroic even in Hell, rises to address his fellow countryman; and, from the same blazing sepulchre, Cavalcante de’ Cavalcanti, fondly believing that it is height of genius alone that leads Dante thus scathless through this blind prison, seeks vainly to see his own Guido with him. Emperor and Pope should lead man to blessedness; but Frederick II. and Pope Anastasius are buried here with the rest (_Inf._ x. 119, xi. 8). The horrible stench that rises from the abyss forces Dante to delay his descent; and, in the pause, Virgil explains the moral structure of Hell, equating the Ciceronian with the Aristotelian division of vice (_Inf._ xi.), as already indicated, and adding a special explanation of how Usury, the breeding of money from money, is a sin against nature, and violence against the Diety.