For today's commemoration of St Andrei Rublev (recently added to the calendar of the Episcopal Church) we turn to Hieromonk Gabriel Bunge's The Rublev Trinity (St Vladimir's Seminary Press 2007).  Fr Bunge, a native of Cologne, Germany, entered the Benedictine monastery of Chevetogne in 1962.  Chevetogne is a "dual-rite" institution, meaning that it houses two distinct monastic communities, one adhering to western patterns of worship and spiritual practices, the other to eastern Christian customs.  Fr Bunge began to live  as a hermit in Switzerland in 1980 and in 2010 he was received into the Russian Orthodox Church. 

The book deals with the icon from a variety of perspectives; the quote below (pp 86-87) shows how it artistically expresses a particular form of trinitarian theology.

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Through his master, Feofan Grek, Rublev had been entrusted with the older christological type.  The main characteristic of this type is that the central angel. identified by a variety of attributes as Christ, the Son, always completely dominates the picture.  He faces the beholder, who looks directly towards him, the other angels being simply accompanying figures, who are often depicted as smaller.  Regardless of the title of the icon, we are formally dealing with an icon of Christ, a distant echo of the early Christian christological interpretation of Gen 18.

In the case of the Greek icons, several of which existed in Russia at all periods, Rublev was, moreover, aware of a more recent, more formally Trinitarian type.  Here, the three angels are as similar one to another as possible.  Attitude, gesture, and posture of the angels are now very marked and allow one to recognize relationships of interaction.  This is achieved mainly through the abandonment of the frontal view, even though the central angel still looks directly at the beholder.  While the christological type retains the biblical background (house, tree, and so on), the Trinitarian type often replaces this with a richly developed architectural setting. 

If one compares Rublev's Troitsa with its predecessors, then it becomes immediately apparent that it reproduces simply neither the one nor the other type.  The form of composition is essentially that of the Trinitarian type, with these striking modifications: 

• The central angel no longer looks at the beholder but at the angel on the left.  Because the gaze of the angel on the left and that of the angel on the right cross one another, the center of gravity moves from the central angel to the one on the left.
• This impression is strengthened because the angels at each side are of the same size as the one in the middle.  This distinguishes Rublev's Troitsa, too, from the icons that immediately preceeded it in the Trinity Monastery.
• From the christological type, Rublev gives the angel in the middle the clothing characteristic of Christ and adds an unusual feature:  the golden clavus (sewn on stripe).  Moreover, he makes the clothing of the other two angels unique and not interchangeable.
• The gestures of the three angels are essentially those of the Trinitarian type, yet with striking modifications.  Originally, the play of the hands was motivated by the objects on the table.  The central angel pointed to the great chalice in the middle of the table; the angel on the left blessed the chalice-bowl standing before him; and the angel on the right stretched out hands towards what was in the bowl standing before him or towards a piece of bread on the table.  These gestures appear in the icons that immediately precede Rublev's Troitsa.  However, in Rublev's icon the table is so small and the figures are so close together that there is no room for any other vessels except for the great chalice in the middle of the table.  The table is bare apart from this bowl.  Over this bowl...the right hand of the central angel points.  The angel on the left raises his right hand both pointing and blessing in the direction of the angel on the right, who for his part drops his hand to the table, a movement that reflects the inclination of his head.  
• Although still in keeping with traditional elements, these gestures clearly express another meaning.  They no longer relate to the food but, in an individual way, to the persons.  In short, Rublev has not simply re-created another icon with christological interpretation:  one individual form with two companions; neither has he created what could be considered a standard Trinitarian icon, that is, three equal, interchangeable forms.  Rather, he has shown three non-interchangeable persons.