The Cappella Portinari was erected in the mid-fifteenth century at the north-east of the Dominican church of Sant’Eustorgio in Milan. Commissioned by the wealthy banker Pigello Portinari, it became the patron’s funerary chapel at his death in 1468. Upon entering the chapel, the viewer is enraptured by the expanse of its dome, richly ornamented with four bands of colour, arranged concentrically around the lantern at the summit.
This painterly decoration invites discussion in relation to contemporaneous understandings of the rainbow in natural philosophy and theology. By the fourteenth century, experts on perspective and meteorology tended to agree that the rainbow comprised four colours: red, yellow, green, and purple or blue, arranged in this order. The dome of the Portinari Chapel features these colours, disposed precisely in this sequence, indicating that its decorative program was indeed intended to be understood as a rainbow.
Based on Genesis 9:12–13, medieval theologians conceived of the rainbow as an intermediary between heaven and earth, and as a reminder of God’s benevolence towards his creation. This connotation was both sustained and complicated by the book of Ezekiel (1:28) and Revelation (4:3), where the image of the rainbow expresses the radiance of God’s glory. While the Genesis passage unambiguously identifies the arcus in the sky as a token of covenant and protection, Ezekiel’s and John’s visions are more ambivalent. The rainbow still manifests divine presence, but its appearance—which eminent medieval theologians, including Isidore of Seville (De Natura Rerum) and Hrabanus Maurus (De Universo), interpreted as evocative of the Last Judgement—is more fearsome than reassuring.
In its dual meaning as token of divine benevolence and reminder of the judgement that awaits all souls, the iridescent cupola of the Cappella Portinari infuses the space with explicit eschatological connotations. These were consistent with the original function of the chapel as a funerary shrine, and also offered a flexible canvas for the theological and scientific reasoning of the Dominican friars of Sant’Eustorgio.
Gitlin Bernstein, JoAnne. 1981. ‘Science and Eschatology in the Portinari Chapel’, Arte Lombarda, 60: 33–40
20 Then Noah built an altar to the Lord, and took of every clean animal and of every clean bird, and offered burnt offerings on the altar. 21And when the Lord smelled the pleasing odor, the Lord said in his heart, “I will never again curse the ground because of man, for the imagination of man’s heart is evil from his youth; neither will I ever again destroy every living creature as I have done. 22While the earth remains, seedtime and harvest, cold and heat, summer and winter, day and night, shall not cease.”
9 And God blessed Noah and his sons, and said to them, “Be fruitful and multiply, and fill the earth. 2The fear of you and the dread of you shall be upon every beast of the earth, and upon every bird of the air, upon everything that creeps on the ground and all the fish of the sea; into your hand they are delivered. 3Every moving thing that lives shall be food for you; and as I gave you the green plants, I give you everything. 4Only you shall not eat flesh with its life, that is, its blood. 5For your lifeblood I will surely require a reckoning; of every beast I will require it and of man; of every man’s brother I will require the life of man. 6Whoever sheds the blood of man, by man shall his blood be shed; for God made man in his own image. 7And you, be fruitful and multiply, bring forth abundantly on the earth and multiply in it.”
8 Then God said to Noah and to his sons with him, 9“Behold, I establish my covenant with you and your descendants after you, 10and with every living creature that is with you, the birds, the cattle, and every beast of the earth with you, as many as came out of the ark. 11I establish my covenant with you, that never again shall all flesh be cut off by the waters of a flood, and never again shall there be a flood to destroy the earth.” 12And God said, “This is the sign of the covenant which I make between me and you and every living creature that is with you, for all future generations: 13I set my bow in the cloud, and it shall be a sign of the covenant between me and the earth. 14When I bring clouds over the earth and the bow is seen in the clouds, 15I will remember my covenant which is between me and you and every living creature of all flesh; and the waters shall never again become a flood to destroy all flesh. 16When the bow is in the clouds, I will look upon it and remember the everlasting covenant between God and every living creature of all flesh that is upon the earth.” 17God said to Noah, “This is the sign of the covenant which I have established between me and all flesh that is upon the earth.”