The Trinity is the Christian doctrine that God, though one, has from all time existed in three divine persons: the Father, Son, and Holy Spirit.1 This doctrine poses some problems for artists, given the animus in Scripture against making images of God.2 Representing the Son as Jesus Christ was declared appropriate by the Second Council of Nicea in 787 because "it provides confirmation that the becoming man of the Word of God was real and not just imaginary."
The Council did not extend this reasoning to the Father or the Holy Spirit.3 However, from the late Middle Ages forward we see images of the Father alone presiding over Annunciation images (example), altarpieces (example), etc.
THE HOSPITALITY OF ABRAHAM
Genesis 18:1-2 says that when "the Lord" (singular) visited Abraham at Mamre the latter looked up and saw three men approaching. As the chapter goes on it continues to alternate between singular and plural. Christian writers took this to refer to the Trinity.4 For Christian artists, the story provided a neat solution to the problem of representing the Godhead. By picturing what was visible to Abraham they could direct the viewer's mind to the invisible reality of God's presence at Mamre.
Early images of the Hospitality of Abraham emphasize the divinity represented by Abraham's visitors by picturing him as bowing to them in adoration and bringing forth what was in effect a burnt offering. In a mosaic panel from the 5th century the visitors radiate light in the upper register and are set against a gold background in the lower. The mosaic shown at the top of this page, from the 6th century, emphasizes the sacrificial character of the roasted calf that Abraham offers on the left by parallelism with Isaac and the ram, the sacrificial victims on the right.
Offering such a strong yet subtle way of calling the Triune God to the onlooker's mind without suggesting that he can be seen with mortal eyes, the Hospitality of Abraham has continued to be the Eastern churches' primary way of presenting the Trinity. In later centuries the three men were often shown as angels with wings (example), a choice most likely due to a desire to obviate any thought that the three figures represent the Father, Son, and Holy Spirit individually.
An influential icon by Andrei Rublev in 1410 drastically reduces the elements in the Hospitality of Abraham. Abraham, Sarah, and the calf are gone, leaving only the three angels, the table, and a softly rendered tabernaculum in the background.
THE THRONE OF MERCY
Three new ways of representing the Trinity developed in the West in the Middle Ages. Each breaks with the taboo on portraying the Father, but two of them do so on the basis of scriptural authority. The first is the Throne of Mercy, which visualizes John 3:16, "God so loved the world, as to give his only begotten Son; that whosoever believeth in him, may not perish, but may have life everlasting."
In this iconographic type the Father presents his dying Son on the cross to the viewer. On the cross sits a dove, the symbol of the Holy Spirit because when he was baptized Jesus "saw the Spirit of God descending as a dove" (Matthew 3:16, c.f. Mark 1:10, Luke 3:22, John 1:32). Beneath the cross, the "world" that will gain "eternal life" is represented by either a mappa mundi orb (as in this example) or a small model of Golgotha with Adam's skull, as in the first picture on the right.
The earliest example I have seen so far is this miniature sculpture, unfortunately with pieces missing, in a Vierge Ouvrante from 1300.
In 15th century works the The Throne of Mercy is sometimes merged with other iconographic types, for example with the Crucifixion and Death of Jesus in this example or with the Annunciation in this one. In a Spanish altarpiece of the period it mediates between an upper panel representing the Crucifixion and a lower one depicting St. Michael's victory over Satan.
One interesting variant from the 19th century introduces a note of exuberance to the type while breaking out of the plane of the painting.
THREE IDENTICAL MEN
The earliest known image of the Trinity presented three very similar men, one of them seated on a throne, creating Eve from Adam. However, this way of picturing the Trinity was almost never seen again until the 16th century (example). It then gained currency, especially in areas colonized by Spain (as in the second picture at right) and in images of the Coronation of Mary (example). However, it was condemned in the 18th century by Benedict XIV and is rarely seen nowadays.5
A related iconographic type had a single human figure with three faces. The earliest example I have seen is a 13th-century fresco from Perugia. This type was attacked in the 16th century by Molanus and forbidden in the 17th by Urban VIII.6
THE SON SITTING AT THE RIGHT HAND OF THE FATHER
Perhaps the Trinity image most often seen today is the one that seats the Son with a cross at the right hand of the Father, with the Holy Spirit between them as a dove emitting light rays, as in the third picture at right. Placing the Son at the Father's right hand responds to a rich vein of scriptural references.7 The earliest example of this type that I have seen is a stone relief from the 16th century. Like almost all subsequent exemplars it makes the Father an old man with a beard, a choice that could be explained by the reference to God as "the Ancient of Days" in Daniel 7:9, 13, 22 and in Revelation 1:14 as having hair "as white … as snow."
This iconographic type is often merged with other subjects. For example it is in the upper register of the central panel in an 18th-century Greek triptych, while the Virgin Orant is in the lower register. In the dome of a chapel in Ravenna, the Trinity thus presented receives St. Anthony of Padua into Heaven. A painting in San Moisè, Venice, uses the same iconography for St. Stephen's vision in Acts 7:56.
In Orthodox versions the Son holds a book open to the viewer. A geometrical frame will close off the image of the dove from the Father and Son figures (example), perhaps reflecting Orthodox objections to the Latin formulation of the Nicene Creed, which says the Holy Spirit "proceeds from the Father and the Son."
Various symbols have been devised to express the trinite and invisible God, such as a triangle within a circle, the "Trinity shield," and the Tetragrammaton in a triangle. In Eastern churches after the Council of 1156 the Hetoimasia or "Prepared Throne" symbol was installed in proximity to the altar. This symbol had a throne to represent the Father, a dove for the Holy Spirit, and for the Son a book and a selection of instruments used in his Passion – the spear, the nails, the sponge, etc. The original purpose of this symbol was to emphasize the teaching that Christ's redemption of mankind through the Cross was predestined from all time. The Council proposed placing it near altars in order to emphasize a second doctrine that it affirmed: that in the Eucharistic liturgy, Christ's sacrifice is offered to the entire Trinity, not just to the Father and Holy Spirit as some had suggested.8
Prepared in 2015 by Richard Stracke, Emeritus Professor of English, Augusta University. Revised 2016-09-17, 2017-02-01.
The Trinity in a 6th-century Hospitality of Abraham mosaic: Detail from the north wall of the chancel at the Basilica of San Vitale, Ravenna