Medieval philosophers developed a theory of light and color that stemmed from their theory of aesthetics. This changed the course of art – especially sacred art – forever, resulting in a new style of church architecture and the advent of large stained glass windows. The medievals saw a connection between the light of the sun and God, and consequently strove to incorporate as much light as possible in their art and especially in their churches. The first church that was built in such a way was Saint Denis in Paris, which would become the birthplace of the Gothic. The medieval concepts of the aesthetics of light and color were extremely important in art and changed the future of church architecture forever.

There are several ancient sources from which this medieval concept originated. Several ancient cults, including the pagan worshippers of Baal and the Egyptians, worshipped a sun god. In Greek philosophy, Plato wrote of the ‘“Sun’ of the Ideal, the Good.”[1] He referred to the sun as “the offspring of the good,” using it as an analogy for the intellect.[2] The neo-Platonists continued this idea of a connection between the divine and the sun; Plotinus wrote that “simple beauty of a color is derived from a form that dominates the obscurity of matter and from the presence of an incorporeal light that is reason and idea.”[3] Pseudo-Dionysius and Saint Augustine later adopted this theory and carried it into Christian tradition.

The writings of Pseudo-Dionysius formed the foundation of the medieval theory of light and color. He wrote that the sun “is the visible image of the Divine Goodness” from which the Good is derived: “wherefore the Good is described by the name of ‘Light,’ being the archetype thereof which is revealed in that image.”[4] Just as the sun illuminates everything with its light, so does God illuminate all things with the light of His Goodness. For this reason, Dionysius frequently referred to God as “lumen, fire, or the fount of light.”[5] Dionysius’ writings on God as light would have a profound impact on medieval art and architecture, as well as on future philosophers and theologians.

Saint Augustine also wrote of the Christian concept of God as light. He frequently referred to God as the “light of my heart.”[6] Saint Augustine is especially known for his doctrine of illumination, which was heavily influenced by the Platonic view of the sun. He wrote that the soul “must be enlightened by another light [i.e., a heavenly light], that it may be partaker of truth.” This other light of which he spoken is God Himself.[7]

In the Middle Ages, saints, poets, and philosophers alike compared God to light. In his Divine Comedy, Dante wrote of the “light freely granted to us by the Supreme Goodness…, light which fits us to see Him.”[8] Saint Thomas Aquinas wrote that Christ “is the light and splendor of the intellect.”[9] He further wrote that beauty exists in the world by virtue of forms participating in the divine light.[10] “Transparent bodies” can transmit this light in the world. Saint Bonaventure developed a complex theory of light, identifying three individual aspects of it: “lux, lumen, and color or splendor.” Lux was light itself, and lumen was the light conveyed by the transparent bodies travelling “through space.” Color referred to the light of “terrestrial bodies,” while “splendor was the light of luminous bodies.” Both color and splendor were reflected through opaque bodies.[11] Thus, the topic of light was of great interest in the Middle Ages.

In the early 12th century, Abbot Suger of Saint Denis read the writings of Pseudo-Dionysius. The philosopher’s teachings on the concept of light especially fascinated Suger, who erroneously believed that he was reading the work of Saint Denis. Suger sought to make Dionysius’ concepts of light “practical and applicable.” He believed that light could “transport” the faithful “to a more heavenly place.”[12] In order to bring this about, he developed a new form of church architecture, whereby the Gothic style was born, changing the style of churches forever.

The previous Romanesque style of architecture allowed little natural light to enter the churches. The walls were heavy stone with small windows spaced widely apart; large pillars inside supported the heavy weight of the ceiling, blocking the light even further. Suger wanted to “open up the space and… allow light to flood in.”[13] In his quest to accomplish this, Suger made several advancements in church architecture. Instead of the thick stone walls, he used pointed arches inside the church and flying buttresses on the outside to support the weight of the ceiling. This enabled him to insert large stained glass windows in the walls, allowing light to fill the church. The flying buttresses also meant that smaller pillars were needed to support the ceiling inside; these smaller pillars obstructed the light much less than did the larger pillars of the Romanesque period. The new church of Saint Denis was a completely new style of architecture that allowed for a great deal of light to fill the church.

Another aspect of medieval Christian wisdom that Suger incorporated in his rebuilding of Saint Denis was the philosophy of color. In the early Middle Ages, the philosopher Hugh of St. Victor wrote that “bright color” is a vital aspect of beauty.[14] During this time, there was a strong emphasis on the importance of simplicity of color, relying on the strength of the light through the glass to illuminate these simple colors and create a heavenly atmosphere. Abbot Suger compared stained glass to the description of the New Jerusalem in the Book of Apocalypse in the Bible:

[T]he holy city, new Jerusalem coming down from God out of heaven… having the glory of God, and her light like a most precious stone, even like a jasper clear as crystal… and the city was pure gold, like clear glass… whose foundations were garnished with all manner of gems.[15]

In the beautiful colored light reflected through stained glass, Suger saw a means of transporting the faithful to a greater awareness of spiritual realities. Brilliancy of color, along with light, was “essential” to the sacred space in Suger’s opinion.[16] Thus, it was important to Suger not only that churches be filled with light, but also that this light enter the church through colored stained glass.

The colors of the glass are symbolic in themselves. Red symbolizes “the blood of Christ… [and] the martyrdom of saints.” Blue symbolizes Our Lady, “heaven, hope, sincerity, and piety.” Green symbolizes nature, “growth and rebirth, [and] life over death.” Violet symbolizes penance, truth, love, and suffering.[17] White symbolizes God’s divinity, as well as purity, chastity, and eternity. “[B]lack and yellow signif[y] penitence and sorrow.”[18] Yellow is also used in halos and depictions of the Gates of Heaven, as well as for symbolizing divinity and glory. Purple symbolizes suffering and royalty.[19] These symbolic colors can be seen in the stained glass windows at the Basilica of Saint Denis, as well as in other medieval Gothic cathedrals.

The philosophy of light and color is of great importance in medieval Christian wisdom and sacred art. Like many aspects of philosophy, the concept of the sun symbolizing a deity became adopted into Christian theology, and the writings of Saint Augustine and Pseudo-Dionysius made it a popular concept for the medievals. It especially influenced Abbot Suger, who became the Father of the Gothic in recognition of his unprecedented ideas on church architecture. The Basilica of Saint Denis, the birthplace of the Gothic, was the first church to embody the medieval concepts of light and color; many more followed, and its influences can be seen even in churches built today. Thanks to the writings of the Christian philosophers on the significance of light in sacred spaces, churches are now filled with light streaming in via beautiful stained glass windows, a visible symbol of the heavenly realities that are present there.

Tree of Jesse Window at the Basilica of St. Denis in Paris, circa 1144, stained glass[20]

The artist is unknown, but the window is believed to have been made around the time Abbot Suger’s rebuilt the church.[21]

This window depicts the Jesse Tree, which is inspired by the words of the Prophet Isaias: “And there shall come forth a rod out of the root of Jesse, and a flower shall rise up out of his root” (Is 11:1 DRB). Jesse, King David’s father, is depicted at the root of the tree; Mary and Jesus are at the very top of the tree, separated from Jesse by three kings. This is an early example of the medieval concept of light, as this large window is one of many in the basilica of Saint Denis. The choice of colors in the window is also symbolic, demonstrating the medieval philosophy of color. The glass behind the figures is blue, which symbolizes heaven. The figures themselves are clothed in hues of red and green – red symbolizing sacrifice and martyrdom, and green symbolizing growth and rebirth.

[1] Umberto Eco, Art and Beauty in the Middle Ages (New Haven: Yale University, 2002), 47.

[2] Plato, Republic, 6.508b, in Plato in Twelve Volumes, Vols. 5 & 6, trans. Paul Shorey (Cambridge, MA: Harvard University, 1969).

[3] Plotinus, I.6, quoted in Michael R. Spicher, “Medieval Theories of Aesthetics,” at Internet Encyclopedia of Philosophy, iep.utm.edu.

[4] Pseudo-Dionysius, Dionysius the Areopagite: On the Divine Names and the Mystical Theology, trans. Clarence Edwin Rolt (Grand Rapids: Christian Classics Ethereal Library), 4.4

[5] Eco, Art and Beauty, 47.

[6] Augustine of Hippo, The Confessions of Saint Augustine, trans. E. B. Pusey (Salt Lake City: Project Gutenberg, 2013), Book I.

[7] Augustine, Confessions, Book IV.

[8] Dante, The Divine Comedy: Vol. 3: Paradisio, trans. John D. Sinclair (New York: Oxford University, 1981), Canto XIV, p. 203.

[9] Thomas Aquinas, Summa Theologiae, I, q. 39, a. 8, respondeo.

[10] Michael R. Spicher, “Medieval Theories of Aesthetics,” at Internet Encyclopedia of Philosophy, iep.utm.edu.

[11] Eco, Art and Beauty, 50.

[12] Beth Harris and Stephen Zucker, “Birth of the Gothic: Abbot Suger and the Ambulatory at St. Denis,” at Khan Academy, www.khanacademy.org.

[13] Harris and Zucker, “Birth of the Gothic.”

[14] ST, I, q. 39, a. 8, respondeo.

[15] Patrick Hunt, “Abbé Suger and a Medieval Theory of Light in Stained Glass: Lux, Lumen, Illumination,” at Archive (29 January 2006), at www.web.archive.org.

[16] Virginia C. Raguin, Stained Glass: From Its Origins to the Present (New York: Harry Abrams, 2003), 14, quoted in Hunt, “Abbé Suger.”

[17] Martin Faith, “Symbolism Behind Stained Glass Color in Churches,” at Scottish Stained Glass, www.scottishstainedglass.com.

[18] Eco, Art and Beauty, 54.

[19] Faith, “Symbolism Behind Stained Glass Color.”

[20] “Excerpts from De Administratione, c. 1144-1148 by Abbot Suger of Saint Denis,” at SLPS, www.slps.org.

[21] Marilyn Mitchell, “Fitting Issues: The Visual Representation of Time in Family Tree Diagrams,” Sign Systems Studies 42, no. 2 (2014), 253.

Works Cited:

Augustine of Hippo. The Confessions of Saint Augustine. Trans. E. B. Pusey. Salt Lake City: Project Gutenberg, 2013.

Dante. The Divine Comedy: Vol. 3: Paradisio. Trans. John D. Sinclair. New York: Oxford University, 1981.

Eco, Umberto. Art and Beauty in the Middle Ages. New Haven: Yale University, 2002.

“Excerpts from De Administratione, c. 1144-1148 by Abbot Suger of Saint Denis.” At SLPS, www.slps.org.

Faith, Martin. “Symbolism Behind Stained Glass Color in Churches.” At Scottish Stained Glass, www.scottishstainedglass.com.

Harris, Beth, and Stephen Zucker. “Birth of the Gothic: Abbot Suger and the Ambulatory at St. Denis.” At Khan Academy, www.khanacademy.org.

Hunt, Patrick. “Abbé Suger and a Medieval Theory of Light in Stained Glass: Lux, Lumen, Illumination.” At Archive, 29 January 2006, at www.web.archive.org.

LaFortune, Chantal. “Light and Color in Medieval Christian Wisdom and Art.” PHH/SAI 560 Essay: Holy Apostles College & Seminary, 2022.

Mitchell, Marilyn. “Fitting Issues: The Visual Representation of Time in Family Tree Diagrams.” Sign Systems Studies 42, no. 2 (2014): 241-280.

Plato. Republic. In Plato in Twelve Volumes, Vols. 5 & 6. Trans. Paul Shorey. Cambridge, MA: Harvard University, 1969.

Plotinus, I.6. Quoted in Michael R. Spicher. “Medieval Theories of Aesthetics.” At Internet Encyclopedia of Philosophy, iep.utm.edu.

Pseudo-Dionysius. Dionysius the Areopagite: On the Divine Names and the Mystical Theology. Trans. Clarence Edwin Rolt. Grand Rapids: Christian Classics Ethereal Library.

Raguin, Virginia C. Stained Glass: From Its Origins to the Present. New York: Harry Abrams, 2003. Quoted in Hunt, Patrick. “Abbé Suger and a Medieval Theory of Light in Stained Glass: Lux, Lumen, Illumination.” At Archive, 29 January 2006, at www.web.archive.org.

Spicher, Michael R. “Medieval Theories of Aesthetics.” At Internet Encyclopedia of Philosophy, iep.utm.edu.

Thomas Aquinas. Summa theologiae. 2nd ed. Trans. Fathers of the English Dominican Province. At New Advent, www.newadvent.org.