This article is taken from the August/September 2022 issue of The Critic. To get the full magazine why not subscribe? Right now we’re offering five issues for just £10.

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Dazzling light is a manifestation of the divine shared across many religions. We only need think of Diwali, the Hindu five-day autumn festival of lights or the Jewish holiday festival of Hanukkah held over the course of eight days and nights. Light also occupies a prime place in Christianity and Islam. The primacy of light in creation is manifest at the beginning of the Bible in which God brings light where previously there had only been darkness. In the Quran light is not just created by God but is identified with God’s presence: “God is the Light of the heavens and earth … God guides whoever He will to his Light.”

Dante’s treatment of light is the supreme manifestation of his complex conjunction of deep learning and soaring imagination

Optical science in mediaeval Europe drew heavily on Islamic optics in Latin translation, above all the De Aspectibus (On Appearances) by Ibn al-Haytham (Alhazen) in the eleventh century, which is one of the great works of science. Al-Haytham embraced the mathematical, physical and anatomical aspects of earlier Greek and Roman traditions, with the addition of his own experimental bent. Under the rubrics of direct illumination, reflection and refraction, the behaviour of light and the functioning of sight are analysed exhaustively.

Not least he deals with the “errors of direct vision and their causes”. Errors arise from the limitation of sight in the face of extreme effects that lie “outside the range of moderateness”, as when something is too far away, too bright or too dark, visible for too short a time, or too fast (like a spinning top). That phenomenon “outside the range of moderateness” plays a crucial role in Dante’s Divina Commedia.

Dante is the most philosophical, theological, visionary and scientific of poets. His treatment of light is the supreme manifestation of his complex conjunction of deep learning and soaring imagination. On one hand his understanding of light as a phenomenon is what we would call scientific — based on a considerable grasp of medieval optics. On the other, his poetic and theological vision of light is full of transcendent rapture.

His engagement with the science of seeing is already apparent in his earlier books of poetry. The first is the Vita Nova (or Vita Nuova, New Life), which was composed about 1292; the second is the Convivio (Banquet), written in the early years of the following century.

Although the Vita Nova is visionary and metaphysical in tone, accompanied by fervent biographical reflections, there are signs of the optics to come in the Commedia. Expressing his total devotion to Beatrice, he explains in his commentary on his own verses that the image of his deceased beloved “had been situated midpoint in the straight line that proceeded from that most gracious lady, Beatrice, and reached its end in my eyes”. This alludes to the optical theory that clarity of sight was achieved by those straight rays that arrived perpendicularly at the surface of the eye, above all the ray that passes precisely through the central axis of the pupil and eye.

We also find his first reference to effects that lie outside the “range of moderateness”:

 

In her countenance appear such things

As exhibit a part of the joy of Paradise.

I mean in her eyes and in her sweet smile,

For here Love bears them as if to his lair.

They overwhelm our intellect,

As a ray of sunlight does weak vision.

 

In his commentary, Dante comments that “here we must understand that in a certain way these things dazzle our intellect, in as much as certain things are affirmed to exist which our intellect cannot observe, that is to say God, eternity, and primal matter”. The stakes go far beyond terrestrial optics.

Dante explains in his commentaries in the Convivio how the eye actually functions. The passage that images make through the air and into the eye is “completed” in the water (the aqueous humour) within the pupil of the eye:

 

because that water has a boundary — almost like a mirror, which is glass backed by lead — it cannot pass any further but is arrested there like a ball that is stopped when it strikes something, so that the form, which cannot be seen in the transparent medium, now appears lucid and defined … The visual spirit passes from the pupil to the front of the brain where is the sensitive power, where it is represented without passage of time, and thus we see it.

 

This is an effective simplification of the process that the mediaeval specialists in optics had gleaned from Islamic science.

the poet’s acts of seeing, which he describes vividly, are regularly cast in terms that are consistent with mediaeval science

Dante’s integration of science into his poetic vision reaches its apogee in the Divina Commedia, written during the first and second decades of the fourteenth century while he was in political exile from his native Florence. In the Commedia, the poet’s acts of seeing, which he describes vividly, are regularly cast in terms that are consistent with mediaeval science. Unsurprisingly, light features little in the punitive gloom of Inferno. There are encouraging glimpses in Purgatorio, but it is in the Paradiso that light comes into its own. In his journey through the celestial spheres with his beloved Beatrice, Dante continually struggles to withstand escalating visions of intense light.

Somehow, in telling the story, Dante merges scienza and poesia; intelletto and fantasia. One example, from the beginning of the Paradiso can stand for many:

 

Beatrice had to her left flank

Turned round to look at the sun:

An eagle never looked at it more steadily.

And as the second ray always issues

And rebounds from where their first ray struck,

Just like a pilgrim who wishes to return,

So from her action, infused into my eyes

By my imagination, my action was enabled,

And I fixed my eyes on the sun other than as we can do.

 

The two references combine science and legend. The rebounding of a light ray along a set course from the point at which it strikes a surface provides the foundation for the science of reflection. The eagle refers to the animal tales in the mediaeval Bestiary in which eagles are credited with being able to stare directly at the fierce radiance of the sun.

Dante’s reaction to the dazzling glare of divine light oscillates between his being blinded to an enhanced ability to see what the eyes cannot normally tolerate. Crucially, the extension of his sense of sight is facilitated by Beatrice. She explains that his hard-won knowledge of optical science on earth simply does not work in the heavenly realm.

In his climatic vision of heaven, Dante is miraculously enabled to see what cannot be seen:

 

My sight in breadth and height

Was not confounded, but took in

The full extent and nature of the jubilation.

Nearness and distance adds nothing, takes away nothing,

Because where God governs without an intermediary

Natural law holds no sway.

 

Even here a scientific analogy is adduced. He compares the sublime ineffability of the Trinity — unseeable with his rational eye — to the mathematicians’ traditional inability to “square the circle” (to devise a formula for a circle precisely equal in area to a given square).

Ultimately there are things that lie beyond the most enhanced scope of human vision and visualization. At the very end of the Commedia, even Dante’s alta fantasia (high imagination) fails, and all that is left is to surrender totally to “the love which moves the sun and the other stars”.

How were painters to emulate Dante’s verbal evocation of the transcendence of divine light? Dante can activate our mind’s eye and let us envisage blinding radiance. In describing the brightest of lights the painter is limited to the material brightness of white pigment on a palette. In the Renaissance, the traditional use of gold to evoke divine light was discouraged. Surely this was one area in which the poets must triumph in the paragone — in the courtly debate about the merits of the various arts. Leonardo famously insisted that the poet could never emulate the painter’s description of natural appearance. But, the Dantesque poet could reasonably ask, what about the “description” of the unseeable?

In describing the brightest of lights the painter is limited to the material brightness of white pigment on a palette

Painters adopted a variety of stratagems to portray divine light within scenes that were set up naturalistically. The trick was to make it look as if light was doing something that stood outside the naturalistic framework. A miraculous effusion of light could move in contradiction to the natural light flow in a scene or disobey natural law, as when Michelangelo’s St Paul in the Capella Paolina falls from his horse and cannot fend off Christ’s shaft of blinding light with his raised hand. Divine light, as Beatrice stressed, does not obey earthly laws.

The Renaissance artist who best succeeds in evoking divine dazzle was neither of the known experts in Dante, Michelangelo or Leonardo. Rather it is Raphael.

We tend not to think of Raphael as an intellectualising artist in the same league as the Platonic Michelangelo and Aristotelian Leonardo. However, there is good evidence that points to Raphael’s direct dialogue with Dante. His father, Giovanni Santi, an underrated painter, was also a poet and author, whose chief composition was a long Rhyming Chronicle in honour of Federico da Montefeltro, Duke of Urbino. It was written in terza rima (3- line units) in overt emulation of Dante.

Giovanni died in 1494, before Raphael’s 12th birthday, but it is reasonable to think that Giovanni’s precocious son was introduced to Dante at an early age. Raphael himself aspired to write poetry. There are six rough drafts for sonnets on drawings connected with his frescoes in the Stanza della Segnatura in in the Vatican early in the second decade of the sixteenth century.

There is good evidence that points to Raphael’s direct dialogue with Dante

One of the murals was devoted to poetry, and portrayed muses and authors, ancient and modern, congregated on Mount Parnassus under Apollo’s command. The stern-jawed Dante was of course present. Dante also features in the Disputa, devoted to theology, and is the only historical person to warrant two appearances.

From the time of the Disputa, Raphael explored a series of Dantesque dazzles. The obvious pictures to look at are the Sistine Madonna from c.1514, with its dazzling corona of vaporous cloud-angels, and the Transfiguration, his final painting, in which the three disciples on Mount Tabor are stunned optically and physically by the irresistible light emanating from the whiteclad Christ.

We will look at two less prominent paintings, the Liberation of St. Peter from Prison from 1514, and the Vision of Ezekiel from about two years later. They show the deep penetration of Dantesque motifs in paintings on different scales. The Liberation occupies a wall in the Vatican, while the tiny Ezekiel is an intimate painting, presumably undertaken for a pious connoisseur. The miraculous release is described in the Acts of the Apostles.

 

Peter was sleeping, bound with two chains between two soldiers … Now behold, an angel of the Lord stood by him, and a light shone in the prison; and he struck Peter on the side and raised him up, saying, ‘Arise quickly!’ And his chains fell off his hands. Then the angel … said to him, ‘Put on your garment and follow me.’ So he went out and followed him, and did not know that what was done by the angel was real, but thought he was seeing a vision.

In the field to the left of the intruding window, Raphael has differentiated three distinct types of light source: the soft glimmer from the rising sun; a crescent moon crossed by a streak of dark cloud; and a blazing torch. The rearmost soldier on the left has seen the divine light, presumably through a window of the cell — to his own cost. His armoured companions are belatedly stirring into action. In the corresponding space to the right, the luminescent angel leads the dazed St. Peter to freedom, while the sleeping soldiers slump on the steps, their eyes untroubled by the unfolding drama. Their failure to see the divine light recalls the inability of the soldiers in Piero della Francesca’s Dream of Constantine to perceive the light that emanates from the invading angel.

The central space, framed in brutal stone, is a wonderful theatre of light. The blast of angelic light off the steely armour of the guards, and the rebounds of light from the walls, are described with astonishingly concise precision, again reminiscent of Piero della Francesca. The prominence of Peter’s dark fetters (vincoli) corresponds to the Biblical account and alludes to the Roman church of San Pietro in Vincoli where Julius II was Cardinal before his elevation to the Papacy. As emphatically black is the impregnable grille of iron between us and the light, which serves optically to enhance the angel’s luminosity.

The most intense light emanates from the twice-repeated angel. Enveloped almost translucently in fiery orange, he is only partly materialised against the blinding mandorla of gold-white, from which stabbing rays thrust into the darkness. Well might Peter be bewildered by what is happening. We can also well imagine that Dante would have recognised Raphael’s expressive differentiation of types of light and types of seeing and non-seeing.

The small painting of The Vision of Ezekiel was a star in the National Gallery’s Raphael exhibition. It demonstrates that comparable effects can be intensely realised in an intimate manner. It is only 30cm (12 ins) wide. Ezekiel’s own account of his vision is prolonged, complicated and difficult to condense into a single image, particularly within such a small compass. Raphael has synthesised the vision into a stern but benign God the Father born aloft weightlessly by two infant angels of a tangible kind and surrounded by the winged symbols of the four evangelists: the lion of St. Mark, the angel of St. Matthew, the eagle of St. John and the ox of St. Luke. They are realised with astonishing virtuosity.

From a radiating glare above God’s head, we are treated to a Dantesque explosion of gold light, which self-combusts into white formlessness

From a radiating glare above God’s head, we are treated to a Dantesque explosion of gold light, which self-combusts into white formlessness. It is fringed by darkish clouds which evaporate into notably elusive cloud-angels, only just visible. Some heads are only described by incisions in the priming. At the lower left of the midground hill, which supports energetic trees, rays of light dart through an aperture in the cloud to strike two tiny persons (about 6mm high), accompanied by a horse. The figure with upraised arms is Ezekiel.

It is only gradually that we realise how spatially illogical is the scale of things in the tiny picture. The base of the clouds that support the central participants is actually behind the central tree at the base of the panel. If we push back the floating figure-group to the depth of the summit of the hill, it becomes a massive apparition. Recall Beatrice’s anti-perspective principle that “natural law holds no sway” in the transcendent realm of heavenly visions. Through a conscious play on contradictory scales, a tiny picture achieves a dizzying level of monumentality.

We can well imagine that Dante would have recognised Raphael’s expressive differentiation of types of light and types of seeing, and not being able to see clearly at all. In the context of a paragone with Dante’s Paradiso, Raphael may perhaps allow us to declare a draw on behalf of painting.