The pages of Pseudo-Dionysius the Areopagite (fifth to sixth centuries), which influenced the whole of medieval aesthetics, show a strong neoplatonic influence. This can be seen in Celestial Hierarchy:
I believe, then, that fire manifests what is most divine in the celestial minds; for the holy authors often describe the super-essential and formless essence—which has no form at all—with the symbol of fire, since it has many aspects of the divine character, if such can be said, insofar as it can be found in visible things. In fact, the sensitive fire is found, so to speak, in all things and passes through all things without mingling with them, and is separate from everything and at the same time, being all-luminous, remains, as it were, hidden, unknown in its essential nature—until it is placed before a material toward which it can demonstrate its own action—it cannot be taken hold of, nor seen, but it takes hold of everything. (chapter 15)
Medieval perceptions of beauty are dominated by concepts of clarity and luminosity, as well as proportion. Cinema and video games encourage us to think of the Middle Ages as a succession of “dark” centuries, not only metaphorically but also in terms of nocturnal colors and dark shadows. Nothing could be more wrong. People in the Middle Ages certainly lived in dark spaces—forests, castle corridors, small rooms faintly lit by their fireplaces; but apart from the fact that they were people who went to sleep early and were more accustomed to the day than the night (of which the Romantics would be so fond), the Middle Ages was a time of bright hues.
It was a period that identified beauty with light and color (as well as with proportion), and this color was always elementary, a symphony of reds, blues, gold, silver, white, and green, without subtleties and half-tones; the splendor is generated from the overall effect rather than deriving from a light that envelops things from outside or exalts the color beyond the outlines of the figure. In medieval miniatures the light seems to emanate from the objects.
In medieval poetry this sense of radiant color is always present: the grass is green, blood is red, milk pure white, and a pretty woman, in the words of Guido Guinizzelli, has a “a face of snow colored in carmine” (not to forget, later on, Petrarch’s “clear, fresh, sweet waters”).
Fire animates the visions of mystics, in particular the writings of Hildegard of Bingen. See, for example, Liber scivias:
I saw a dazzling light and in it a human form, the color of sapphire, which was all ablaze with bright gentle fire, and that splendorous light spread throughout the whole bright fire, and this fire was bright with that splendorous light, and that light was dazzling and that fire bright with the whole human form, producing a single glow of matchless virtue and power . . . The flame consists of a splendid clarity, an inherent vigor and a fiery ardor, but the splendid clarity possesses it so that it is resplendent, the inherent vigor so that it endures, and the fiery ardor so that it burns. (book 2, part 2)
Not to forget the visions of brilliant light in Dante’s Paradise and which have been depicted in their maximum splendor by a nineteenth-century artist, Gustave Doré, who sought (as only he could) to depict those scenes of radiance, those flaming vortexes, those lamps, those suns, that clearness that hides “like an horizon brightening with the dawn” (canto 14, line 69), those white roses, those rubicund flowers that shine out in the third part of The Divine Comedy, where even the vision of God appears like an ecstasy of fire:
Within Its depthless clarity of substance
I saw the Great Light shine into three circles
in three clear colours bound in one same space;
the first seemed to reflect the next like rainbow
on rainbow, and the third was like a flame
equally breathed forth by the other two.
(canto 33, lines 115–20; translated by Mark Musa)
The Middle Ages was dominated by a cosmology of light. Already by the ninth century John Scotus Eriugena said, “This universal manufactory of the world is a vast lamp consisting of many parts like many lights to reveal the pure species of intelligible things and to sense them with the mind’s eye, instilling divine grace and the help of reason into the heart of learned followers. It is right then that the theologian calls God the Father of Enlightenment, since all things are from Him, for which and in which He manifests himself and in the light of the lamp of his wisdom he unifies and makes them” (Commentary on the Celestial Hierarchy, chapter 1).
In the thirteenth century the cosmology of light put forward by the English churchman Robert Grosseteste built up a picture of the universe formed by a single flow of luminous energy, a source both of beauty and being, making us think of a sort of Big Bang. The astral spheres and natural areas of the elements are created from the single light by gradual rarefaction and condensation, producing the infinite shades of color and the volumes of things. Saint Bonaventure of Bagnoregio (Commentary on the Book of Sentences, book 2, distinction 12, chapters 1 and 2) was to record that light is the common nature found in all bodies, whether celestial or terrestrial; light is the substantial form of bodies, and the more they possess it, the more they are a real and worthy part of existence.
HELLFIRE
But while fire moves across the sky and shines down on us, it likewise erupts from the bowels of the earth, bringing death. Thus, from the very earliest times, fire has also been associated with the infernal depths.
In the book of Job (41:19–21), from the mouth of Leviathan “go burning lamps, and sparks of fire leap out . . . His breath kindleth coals, and a flame goeth out of his mouth.” In Revelation, when the seventh seal is broken, hail and fire come to devastate the earth, the bottomless pit opens up, and from it emerge smoke and locusts; the four angels, set loose from the river Euphrates where they were bound, move with countless armies of men wearing breastplates of fire. And when the Lamb reappears and reaches the supreme judge on a white cloud, the sun burns the survivors. And, after Armageddon, the beast and the false prophet will be thrown into a lake of burning sulfurous fire.
In the Gospels, sinners are cast into everlasting fire:
As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world. The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity; And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth. (Matthew 13:40–42)
Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels. (Matthew 25:41)
Curiously, in Dante’s inferno there is less fire than we might expect, since the poet contrives to think up a whole range of torments, but we may be satisfied with heretics lying in fiery tombs; men of violence plunged into pools of blood; blasphemers, sodomites, and usurers struck by rains of fire; simoniacs shoved head-first into pits, with flames lapping at their feet; and barrators submerged in boiling pitch.