This is the fifth and final part of a five-part article.

The Plan of the Article:¹

Α. MORSE AUDITORIUM, BOSTON UNIVERSITY
              Β. THE PANTHEON, ROME
                             Ξ. HAGIA SOPHIA, CONSTANTINOPLE
Ο. THE ONION DOME, LAND OF THE RUS’
              Ω. BRUNELLESCHI’S DOME, FLORENCE

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Ω. BRUNELLESCHI’S DOME, FLORENCE

Two-edged swords shall be in their hands, to do vengeance among the heathen, punishments among the peoples, to bind their kings with fetters, and their nobles with manacles of iron, to do among them the judgment that is written. (Ps. 149:6–9)

They built the cathedral intending to have a dome, but they didn’t have functional plans for one. A public contest was held, and while competition was fierce, Filippo Brunelleschi beat out his old rival Lorenzo Ghiberti for the commission of building the dome.

What these Florentines had in mind can be seen in the image above. It is a depiction of the Florence Cathedral painted by Andrea di Bonaiuto in the 1360s — hence before even the nave was completed in 1380, to say nothing of the dome which was not built until 1420–1436. This was roughly the project Brunelleschi was commissioned to complete.

Brunelleschi for his part was a prestigious master goldsmith (original profession of several artists of the early Renaissance) who when the contest for designing the dome was announced in 1418 was a 41-year-old sculptor who had not designed a single building.² That was no matter — what the Florentines wanted done, no one in the world had ever done, nor did anyone have any idea how to do it. In their drive to compete with neighboring city-states like Siena and Pisa, their designs for their new cathedral (the construction of which began in 1296) kept growing and growing until the early fifteenth century when they had a massive octagonal hole to fill at the center of their cruciform floor plan.

The scale was unprecedented. The prospective dome would cover a width nearly that of the Pantheon, and the project would begin at the height of Hagia Sophia. Of course the dome on Hagia Sophia was itself begun at (nearly) that height, but it was much smaller in diameter; and the entire building beneath it was designed with it in mind. The Florence Cathedral was not designed with anything in mind other than to be bigger and better than what their neighbors were doing. Its thick octagonal drum was equipped for vertical thrust, but that only. Any functional dome design would have to account for its own lateral thrust, and the Florentines had already ruled out as barbaric any external buttresses recently so popular in the rest of Western Europe.

The clean classical style based on rational geometric forms was more to their taste, and in Brunelleschi they had a man further down that road than they. Renaissance architecture didn’t exist yet, mind you; Brunelleschi is the one who started it. Before his big Florence commission he had spent much time preparing in Rome by studying the ancient monuments and investigating any ruins he could find. The Pantheon of course was still a functioning church, and it was to be a primary influence on him. All the domes he designed later in his career would be hemispherical like the Pantheon, but that wouldn’t be possible on the Florence Cathedral. At Hagia Sophia, when Isidore the Younger replaced the fallen dome in 562, he made it twenty feet taller because that reduced the lateral thrust, shifting weight to the vertical pillars instead. Accordingly in Florence the dome would have to be tall — very, very tall.

Height alone was not going to hold such a structure in place, however. And creating a design that could stand once built was not even the hardest part. Actually building it was the biggest challenge. If you can’t make a dome that can stay up when it’s only partly done, you’ll never get a chance to see if it holds together when it’s finished. The base of the proposed dome was so big and so high, wooden formwork (the usual way vaults were constructed) was not feasible. Brunelleschi alone among the competitors for the commission claimed to be able to build the dome from the bottom up without several forests’ worth of formwork holding it in place, and without it spilling over. The walls of the dome were going to support themselves, and they were going to do it every step of the way.

The council members in charge of the commission along with the other craftsmen wanted to know from Brunelleschi how he intended to do it. He brought them eggs and told them if they could make an egg stand on its end, he’d tell them how he’d build the dome. None of them could do it. The master goldsmith then took an egg and lightly tapped the end, breaking the shell but not piercing the membrane. The egg then stood on its flattened end. Everyone present said with disappointment, “Oh, well we could have done that.” “Yes,” Brunelleschi replied, “and if you knew what I know, you’d be able to build the dome!”³ His fellow Florentines had expected the egg trick to illustrate how the dome was to be built. But Brunelleschi meant it as an object lesson that they had to rely on his genius, unproven though it may be. That was how the dome was going to be built. He may not have known how it was all going to work in practice, but he had the ideas — and he trusted himself to pull it off.

That he was not unjustified in trusting in himself, and that the council was justified for giving him the commission, is known because the dome he built still stands, the largest masonry dome ever constructed. How he pulled it off exactly isn’t entirely known, but many ingenious aspects of its engineering are. The first thing to know is that the dome has two shells, an inner and an outer. You could think of it as a dome inside of a dome (rather than a dome on top of a dome, as seen previously), but you can also see the two shells working together as one dome, the thick walls of which are not solid. Within those walls a network of ribs and bracing that holds the final structure together would have performed the same function as the dome was gradually being built, one layer around at a time.

Of the arched vertical ribs (made of brick), eight main ones are visible on the exterior (covered in marble) at the corners of the eight sides. Hidden in the walls are two more per side. Further, at major stress points there are what look like train tracks made of stone and iron running the full perimeter of the dome. Their job is to brace the walls, containing the lateral thrust like hoops around a barrel. Such action only holds together the inner shell, but that’s good enough. It’s the inner shell that holds up the outer shell, while the outer shell performs the basic function of a roof by keeping out the weather. The hollow space between the shells reduces the weight of the dome.

Even with the ribs and braces, had the bricks in the walls been laid in straight lines, they would not have held; the walls would have collapsed during construction. For one thing, the mortar seams holding it all together (the weakest part of any masonry wall) would have cracked under the stress, causing the structure to topple inward. To prevent this, Brunelleschi used a so-called herringbone pattern of bricklaying that he learned from antique Roman sites but was not generally known in his day. Herringbone refers to diagonal lines of vertically placed bricks that break the continuity of the mortar seams and prevent them from cracking. These diagonal lines would also bind the eight walls to each other by continuing to spiral upward as they pass through the main ribs on the corners. Another important trick employed is that each line of bricks between the eight main ribs would dip a little in the middle, thereby forming an inverted arch that, along with the herringbone pattern, would help keep the latest layers of masonry from breaking off.⁴

The biggest mystery, though, is how Brunelleschi guided the walls as they were being built such that their arches all joined at the top as they should. There was not any formwork to guide him, and the eight-sided base he inherited from other builders was not even a perfect octagon and had no true center.⁵ It is accepted he probably used ropes to guide the process, but what process he used to guide the ropes, what mathematical or geometrical method, has not been preserved.⁶ Whatever he did worked to a T. The eight sides rise at just the right angles to form a perfect Gothic arch — with its tip leveled off for a perfectly octagonal oculus.

It’s not a hemisphere, but in 1436, sixteen years after he began, Brunelleschi completed the closest form to the Pantheon as was possible. With the dome’s elongated shape, it’s even like its oculus is reaching for a vantage point higher than what ancient Rome could have achieved. That same year the cathedral was consecrated in honor of Santa Maria del Fiore (St. Mary of the Flower) — perhaps reflected in the octagonal oculus at the very apex of the building. The dome was in this condition (without the lantern on top) when in 1439 the Council of Ferrara needed to relocate due to plague and came to Florence till its conclusion in 1445, since which time it has been known as the Council of Florence. The dialogue conducted there between Roman Catholics and Eastern Orthodox produced no fruit, and Hagia Sophia became a mosque in 1453.

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The Lantern

They built the dome intending to put something above the oculus, but they didn’t have functional plans for anything. A public contest was held, and while competition was fierce, Filippo Brunelleschi beat out his old rival Lorenzo Ghiberti for the commission of building the lantern. (After such an historic achievement as the dome, Brunelleschi must have felt awfully insulted to have to submit to another contest for the lantern. Anyways, he won.)

Now, although the consecration and Council of Florence proceeded without the lantern as if it were not essential — indeed, from inside the cathedral, it made little difference — there yet had long been plans for an ornamental structure atop the dome, as evidenced by Andrea di Bonaiuto’s 14th-century fresco (see above). But only in 1446, a decade after the consecration, was the contest held and construction begun. Brunelleschi died just a couple months later, but his plans were eventually carried out, being completed up to the conical roof in 1461.

The marble lantern serves the function of covering the oculus while still allowing light in. When the Pantheon in Rome was built, an uncovered oculus was planned for, and the floor was specially designed to channel rain water into drainage holes. No such foresight was made for the Cathedral in Florence, which began construction in 1296 and didn’t have its dome started until 1420.

But more than a practical function, the lantern serves an essential aesthetic function. In making the dome taller, Brunelleschi did not lengthen the desired hemisphere arbitrarily. In profile the two sides of the dome represent segments from two different circles (see illustrations above and below), a result of classic Gothic arch design known as quinto acuto, or pointed fifth (so named because the radius of each of the circles is four-fifths the total space to be covered, measured from either side).

As a result the arch is not continuous like the Pantheon’s hemisphere but comes to a point. Brunelleschi, still inspired by the Pantheon, leveled the point with an oculus, but the effect of quinto acuto is the same. The shape produced is an image of dualism in that two circles contribute to its arch. This dualism, visually speaking, simply begs to be resolved by a unifying element at its peak. Normally in Gothic vaults that element is the point to which the arches rise. If you remove that point for the sake of an oculus, another unifying element must take its place. The lantern fulfills this aesthetic necessity.

The conical roof of the lantern, moreover, was not the end of Brunelleschi’s design. Atop it he called for a gilded ball and Cross. In 1468 artist Andrea del Verrocchio was commissioned to build the ball, which he made of gilded copper, completing it in 1471. Someone else made the Cross.

Ambiguity in Meaning

I find the entire Florence Cathedral dome, a colossal masterpiece of early Renaissance architecture, especially ambiguous in meaning. On one hand, one could see the dome, the lantern, and the Cross and ball — all built in separate stages, with separate commissions — as representing the three stages of the life in Christ: purification, illumination, and perfection. Since this is Florence just a century after Dante, however, a more appropriate formulation might be Purgatorio, Paradiso, and the Empyrean (the fiery dwelling place of God beyond the spheres of heaven). These three stages correspond more or less with Dante’s three guides in the Divine Comedy, Virgil, Beatrice, and St. Bernard.

At the top, St. Bernard shows us the Cross and the ball symbolizing God and the world, the two natures of Christ, perfection. It is a necessarily humble symbol for the Empyrean. The lantern crowning the oculus, like the light of Beatrice, symbolizes illumination, naturally. As the gateway to the physical heavens, this is a good symbol of the celestial spheres Dante calls Paradiso. And the Gothic arches of the dome along which Virgil leads us symbolize the dualism of the material world ascending in purification around the oculus of spiritual illumination coming from above. It is a towering mountain with an earthly paradise on top, just as Dante describes Purgatorio. (Here’s to keeping any infernal symbolism outside the church.)

We would have in this dome, then, an outline roughly similar to the shape of the onion dome, although the conical roof of the lantern would thus have to symbolize the nous for how it hosts the revelation of an Empyrean God. The oculus borrowed from the Pantheon would no longer carry that symbolic meaning. But then how would one make sense of the interior experience of the dome?

If we can for a moment look past the stunning 16th-century frescoes to consider just the architectural form, we’ll see here (in the image above) something closely akin to what the Pantheon offers: an interior mountain of a hierarchy climaxing in an eye filled with light from a far distant source. If the unseen lantern above indicates the Empyrean God as the source, the churchgoers inside are divorced from that vision. It’s as if they were trapped in a Purgatorio narrative (purification), ever gazing at merely the horizon of a Paradiso narrative (illumination), and cut off from any divine cause. This is not the realized eschatological vision of Christ’s Church that we’ve seen previously.

This dialectic of light rather could be said to form a discouraging trend with what came previously in Western church art, if one wanted to be a cynic about such things. Consider the preponderance of stained glass in many Gothic churches of the West, and compare that form with the classic tesserae mosaics that have never gone out of style in the East.⁷ In a mosaic of tesserae, light reflects from the image itself — the light doesn’t merely bounce off the surface but appears to radiate from within. A symbolic union is thus forged between the two, light and image, aesthetically representing the traditional hesychastic teaching on how divine energies imbue creation.

In stained glass, however, the image and light are thrown apart at a great distance. The detachment is emphasized in the changeable glow of the image, presented as a positive feature of the form. Indeed, according to the more conceptualist consequences of the Scholastic insistence on a divine simplicity that excludes the distinction of essence and energies, the operations of God by which He is known are created effects and not divine. The “light of glory” by which the beatific vision is experienced cannot be identified as Uncreated.⁸ All aesthetic representation thus becomes relativized, and stained-glass images offered for veneration can only stand between their viewer and the source of light, with a great dialectical distance between them, just like the effect produced by the oculus in the Florence Cathedral. As marginal decoration, stained glass indisputably can be an excellent contributor to beauty. As a prominent architectural motif, however — according to this particular theological interpretation — stained glass produces a de-materialized spirituality whereby the bodies of images are to be cherished for their submission to an artificial light that is itself to be cherished specifically for its mutability and detachment from any visible source.

The same relativizing dialectic can be seen to run through Brunelleschi’s work, especially in the domes he got to design from scratch. At the Old Sacristy (built from 1421 to 1440) in Florence’s San Lorenzo Basilica, we can see that Brunelleschi is simply not playing with the same symbolic playbook as the architectural forms that preceded him.

As seen above, gone are most vestiges of Gothic architecture, as Brunelleschi gives himself free rein to imitate the Pantheon with its hemispherical dome and oculus — which! — which he nonetheless places on pendentives over a square space. He repeats this pattern in the Pazzi Chapel, also in Florence (see below). This makes little symbolic sense to me. The pendentives cannot here symbolize the heavens the way they did in Hagia Sophia and countless churches since (including in Italy, in St. Mark’s Basilica in Venice, for example). The presence of the oculus in the upper dome wrecks that. Perhaps the pendentives are the material heavens, the dome is the spiritual heaven, and the oculus is the eye that sees a God who is infinitely beyond that. But is the Word of God incarnate or not? Does the Empyrean God of the West have flesh? As the Pantheon before it, this model of the cosmos suggests a reality without Incarnation. The dome can’t symbolize the incarnate Word of God if there’s a hole poked in it, relativizing it and suggesting that we should look for an absolute beyond it.

Viewed critically, the dome on the Florence Cathedral has the same symbolic meaning. How the interior experience of the dome separates one from the source of illumination and denies the immanence of an incarnate God was discussed above. Even from the exterior, though, the ambiguous meaning of the lantern complicates interpretation. In shape it points upward, toward the ball and the Cross. But its purpose points downward, toward the oculus.

Unlike the onion dome, there is not a continuous curvy line that draws the symbolic meaning down from the Cross and back up to it. Rather the lantern sits on the flat plane of the oculus that segments the structure. The lantern exists as ornament, providing visual manifestation of what is beneath it, the oculus. The hierarchy of meaning and expression is thus overturned.

Principles of meaning in a theistic cosmology should always come from above; the potential to host that meaning with bodies of expression is provided from below. The distinction of heaven and earth, for example, only makes sense as an expression of the higher principle distinguishing Creator and creation. The form of the Florence Cathedral suggests a break in that hierarchy. Not only does the dome below gather around the oculus for meaning, but also the lantern above it is a manifestation of its principle. If the oculus still symbolizes the mind’s eye, it is here an object of idolatry.

But the lantern also points above! It still resolves in unity the duality of the Gothic vault beneath it! Not by accident does this historic building have a Cross on top, as the emphasis on the oculus might suggest. It’s all so hopelessly ambiguous. Yet I feel the entropy of the negative critique pulling my interpretation down, especially as I consider a wider historical context.

In Renaissance Florence, everything high above becomes a material expression of ideas from down below. The dome becomes a monument to human ingenuity and self-reliance, to the ability of man to pull himself up by his bootstraps. (I’ve yet to mention how Brunelleschi invented an all-new hoisting mechanism to lift supplies up to the dome.) This bottom-up, self-supporting design style is reflected fractally in the Italian society’s emphasis on technological progress by means of competition, a dialectic of opposition akin to natural reason. A possible, if more hostile interpretation of the Florence Cathedral dome references precisely that: the oculus symbolizes nought but the light of reason. There’s no theological meaning at all.

It was with an active rational mind that Brunelleschi in his spare time also invented linear perspective in drawing (another thing I’ve yet to mention so far), that innovation which transformed Western sacred art into illusory realism and eye-catching spectacle. Time and again spiritual topics in Renaissance art were used for expressing principles found in material nature. It’s an upside down cosmology that imprisons us on the spheriness of this world with no access to the horizon so vividly depicted by linear perspective.

This Pantheon-like adulation of the world, combined with a Pelagian-like emphasis on human ingenuity — in a Christian civilization — was bound to inspire a dialectical backlash. In iconoclastic opposition to the roundness of all domes, Protestant steeples were about to proliferate across Europe, as if the sphere and axis of the onion dome were divided from each other and made to fight a holy war. Sacramentality became idolatry, so faith became iconoclasm. Steeples are the end of this story.

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Last Judgment

Let me honor one last time the Cross on top of the Florence Cathedral, the one to which the lantern points, the lantern to which the arches lead. Let me reclaim at least the ambiguity of this dome’s meaning, that I may represent it accurately. It is good and evil both. Let God sort out what matters most and for whom. For the sake of those to whom the Florence Cathedral means a good deal, let me take nothing away from that good.

Two sections back, when talking about Hagia Sophia, I occasionally made note of the iconographic interpretations linked with the architectural forms. I tried not to belabor the connections because they have room for variance and need not be determinative. Surely the Muslim insignia seen there today is not authoritative. That hermeneutic caution is especially called for in the Florence Cathedral, where the dome was designed and built on one side of the Renaissance while not till the other side were the interior frescoes painted. Maybe, though, with that caution in mind, we should finish out the article by taking a quick look at those frescoes. Brunelleschi the goldsmith had wanted the dome interior decorated with gold, so these images do not reflect his artistic vision. But they do represent the vision of the people of Florence.

The frescoes were painted from 1568 to 1579 by a team of painters led first by Giorgio Vasari, and then after his death by Federico Zuccari. The theme chosen is one which in Orthodox churches is normally reserved for the back wall by the exit. Michelangelo used it for the wall behind the altar in the Sistine Chapel, and that’s what inspired Vasari. Here it’s the central dome, and I think it’s fairly apt considering the purgatorial context. It is the Last Judgment.

The majority of the dome (see above) is reserved for the saved, but the damned are amply (and vividly) represented in the lower circle at the base.

The section around the oculus (pictured above) was completed by Vasari before his death and depicts the twenty-four elders from Revelation, chapter 4.

This (above) is the central panel facing the nave. Beneath Christ in Glory are the Three Theological Virtues; and beneath them is being crowned the Church Triumphant. Time and Death at bottom are the least frightful images along the dome’s base.

This image is at the base of the dome, dead center facing the altar. Here Lucifer devours Judas, as described at the bottom of Dante’s Inferno.

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That concludes the article. Thank you for reading!

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The Plan of the Article:

Α. MORSE AUDITORIUM, BOSTON UNIVERSITY
α. it began as Temple Israel
              β. dome on a box
                             χ. the risk of collapse
              ο. hemispherical interior
ω. God, heaven, and earth

                             Β. THE PANTHEON, ROME
                             α. the cosmos separate from God
                                            β. the rectangular portico
                                                           χ. the dome and oculus
                                            ο. oculus as mind
                             ω. Christian conversion

                                                           Ξ. HAGIA SOPHIA, CONSTANTINOPLE
                                                           ς. the semi-domes
                                                                          ζ. the pendentives
                                                                                         η. the dome

Ο. THE ONION DOME, LAND OF THE RUS’
α. history and practicality
              β. frame and surface
                             ξ. the Cross
ο. tip as paradise
              ω. potential for inversion

                             Ω. BRUNELLESCHI’S DOME, FLORENCE
                             α. a giant hole to fill
                                            β. self-supporting walls
                                                           ξ. oculus complete
                             ο. the lantern
                                            ω. ambiguity and judgment

1. I call this kind of structure a “ksiasmus.” It is related to the chiasmus, but whereas chiasmus is named after the Greek letter chi (Χ) because of its inverse parallel structure, a ksiasmus has a direct parallel structure and so is named after the Greek letter ksi (Ξ). It is a form not uncommonly found in Scripture. An easy example to point to is the arrangement of the camps of Israel around the tabernacle in Numbers 2. They are listed in the following order: east camp, south camp, central camp, west camp, north camp.
2. By the time Brunelleschi won the contest in 1420, he had begun his first commission, the Foundling Hospital in Florence in 1419, since considered to be the first example of Renaissance architecture for its anti-Gothic rationalism and classicism.
3. See Giorgio Vasari (who I’ve paraphrased liberally), The Lives of the Most Excellent Painters, Sculptors, and Architects, Volume 1, Second Part, “Filippo Brunelleschi.” Online translation from the 1568 edition.
4. See Nova, “Great Cathedral Mystery” (uploaded on YouTube, July 22, 2016).
5. See National Geographic, “How an Amateur Built the World’s Biggest Dome” (YouTube, January 24, 2014), at 1:00.
6. For three theories, quickly sketched, see “How an Amateur,” at 2:20. The Nova video previously cited explains Massimo Ricci’s persuasive flower theory in more depth (with Ricci’s participation).
7. This point of contrast is already suggested in Gardner’s Art through the Ages, standard textbook of art history. From the Tenth Edition, p. 436: “The Gothic architect uses light as a medium, as does the Byzantine, but he uses it in opposite ways. In Gothic architecture, light is transmitted through a kind of diffracting screen of stone-set glass; in Byzantine architecture, light is refracted from myriad glass tesserae set into the hard bed of the wall” (Harcourt Brace College Publishers, 1996; emphasis in the original).
8. See David Bradshaw, Aristotle East and West: Metaphysics and the Division of Christendom (Cambridge University Press, 2004), pp. 242–62.