In Lumine Tuo
The Middle Ages were the age of light. Pseudo-scholars say it were the "Dark Ages", ignoring the creation of Universities, Gothic cathedrals, illuminated books and so on...
In lumine tuo, videbimus lumen
in thy light we shall see light
Ps 35, 10
These words which the Holy Church properly applies to Jesus Christ, Our Lord, can also be analogously referred to the Middle Ages. Because, in the light of those times, which marked the apogee of Christianity, one can contemplate the light of Catholic truth, the "lumen Christi".
"Middle Ages, Dark Ages". That's what the pseudo-scholars on the outskirts of culture say, judging it to be an age of ignorance and fanaticism.
However, it was the so-called age of darkness and ignorance that created the universities. Sorbonne, Cologne, Oxford, Bologna, are some of the great cultural centers that illuminated history.
The Middle Ages, "dark ages", were passionate about light. And it was this passion that built the Gothic cathedrals. What is Gothic style but an insatiable thirst for sunlight and sky light? What is this style if not the power of light united in poetry with a stone?
Georges Duby, in his book Le temps des cathédrales, states that Gothic was born from the theology of light. Suger, abbot of Saint Denis, wanted to make his abbey an architectural work that would express in stone the theology of light, as it is exposed in the work of the pseudo-Dionysius.
According to this author, God is light and each creature is a reflection of divine light. The universe would be like a cascade of hierarchically ordered lights.
Intelligence can ascend this scale of reflections until it reaches the ineffable light of Divinity, for the created leads to the uncreated. God, absolute Light, is more or less veiled and revealed by each creature. This is the key to understanding Gothic, art of luminosity and progressive radiance. The same principles with which scholastic theology recognizes the light of God in the universe are applied in Gothic architecture. And so, the Gothic cathedral is the light of scholastic theology embodied in the poetry of stone, says Duby.
From classical to Romanesque, from Romanesque to Gothic, there is a continuous movement from moonlit night to dawn, and from dawn to light.
All experts agree with this.
"The cathedral is ordered to capture the light and keep it as something transformed, from immaterial, as it was thought to be, in this very rare and subtle matter that is a stained glass window under a very high vault" (F.Cali and S. Moulinier, L'Ordre Ogval).
The stained glass windows, that wonder created by the Middle Ages to "ennoble the light of God, to give it the iridescence of amethyst or ruby, to lend it the colors of heavenly virtues" in the happy expression of Georges Duby, revealed the dissatisfaction medieval with the present world, made less brilliant by the sin of Adam.
It is the "longing" for the light of the original paradise that made the Middle Ages open the great ogival windows of their cathedrals so that the sunlight could penetrate, in bursts and colored, to the tabernacle, where we can find, humbly in the sacred host, the Sun of Angels.
The Middle Ages were not just a stained glass window in history, it was also a golden page of illumination.
In the silence of the abbeys, by the patient hand of the monks, they copied with golden letters the books of the past, adorning the pages of wisdom and science with the light of beauty. Yes, it was the dark ages that created the illuminated books, full of light, grace, life and joy.
Light and joy always come together. And the Middle Ages, in love with light, made sadness the eighth capital vice. Is it any wonder that it carved the smiling angels on the portals of Reims?
It was this passion for light that made medieval poets sing of the brightness, the sun, the clarity, delighting in the color of the universe.
Dante, the supreme poet of the Middle Ages, related celestial glory to light, and hell to darkness.
 Per letiziar là sù fulgor s’acquista,  sì come riso qui; ma giù s’abbuia  l’ombra di fuor, come la mente è trista. On high, joy is made manifest by brightness,  as, here on earth, by smiles; but down below,  the shade grows darker when the mind feels sorrow.
Dante, Divine Comedy, Paradise (link)
And the Middle Ages illuminate all of history with a triple light: the light of truth, justice and beauty.
Light of Truth, which it produced through Scholastica. It was the time of universities.
Light of Justice, that shines on your innumerable saints like the stars of the firmament. It was the time of the abbeys.
Light the Beauty, of your incomparable art. It was the time of cathedrals.
And because the middle ages were intoxicated with light, the "Dark Ages" is the splendor of History and of it one can say:
"In lumine tuo, videbimus lumen"