The transformation of the word's meaning owes much to The Divine Comedy's opening book, Inferno. Having abandoned hope and entered hell, Dante travels through the nine circles of torment. In Canto IX, for instance, he and Virgil enter the Inferno city of Dis ('the city of fire'), which houses the lowest and most grievous circles of hell. Imprisoned here are the most 'accursed spirits': the active (as opposed to passive) sinners. These not only include murderers, blasphemers, traitors and sodomites (Judas, save for the last), but also the enemies of medieval Christendom such as Jews and Muslims.

Fire is employed liberally in the Sixth Circle to scorch the many variations of heretic: 'Here are the heresiarchs with their followers of every sect, and the tombs are much more laden than thou thinkest. Like with like is buried here, and the monuments are more or less hot.' Not all of hell's flames burn so directly or even literally. Running through the Seventh Circle is the 'River of Boiling Blood' which slowly poaches 'whoso doth harm to others by violence'.

The Eighth Circle is practically an enormous and all-too real conflagration in which 'every flame steals away a sinner'.

One of hell's many paradoxes is that the closer Dante draws to its centre in the Ninth Circle, the colder things get: infernal and Inferno don't always go hand in hand, it would seem. Indeed, by the time the poet encounters Lucifer, the 'emperor of that woeful realm', things have got positively glacial: 'his mid-breast issued forth from the ice'.

Having witnessed Lucifer lunching on history's very worst sinners, Judas and Cassius, he performs a peculiar spiritual cartwheel (Lucifer, now upside down, represents a point of complete inversion) and exits the Inferno for good.

It is debatable whether Dante or 17th-century English poet John Milton's hell set the standard for depictions of heated anguish. But read Inferno alongside Gustav Dore's extraordinary, if stomach-churning engravings. They are truly a flaming delight.