Surely Masaccio's depiction of the Holy Trinity in the nave of the Dominican church of Santa Maria sopra Minerva in Florence (1426-28) can be considered one of the first works of the Italian Renaissance. It is also the last work of the master.
We do not know exactly when the work was executed, neither do we know who commissioned it, even though he is represented with his wife in the fresco. The masterpiece is located in an asymmetric position in the nave, near the door that led to the basilica's cemetery. The dogma of the Holy Trinity was very important to the Dominican friars, owners of the church, and this would also explain the prominent position of the work. Apparently, also a theologian worked on the creation of the fresco, probably, Fra' Alessio Strozzi, a humanist philosopher and mathematician who was very popular among Ghiberti and Brunelleschi.
The planning of the work took many months as it needed precise calculations of the proportions and a partial closure of the stained glass window above. The work is fairly well conserved, also thanks to Giorgio Vasari who saved and preserved it after the Counter-Reformation when an new altar was built before it, with a new altarpiece. Thanks to the great Renaissance chronicler the work remained intact until the 1860s when it was "rediscovered".
The principal subject of the fresco is the important iconography of the "throne of grace" which is one of the most diffused ways of representing the Holy Trinity: the Father holds his Son who is crucified, (usually, and in this case) the Holy Spirit is between them. This iconography was rather popular in the Florentine Renaissance. The theological source can be found in Isaiah 16,5 and in the Letter to the Hebrews 4,16: Let us then approach God’s throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need. Masaccio's was the first representation of this iconography on a monumental scale and it was also the first to use such a realism and advanced use of the perspective. The master also melted in it more iconographic motifs such as Mary and John at the feet of the Calvary. Usually, God the Father would be seated on a throne, in order to evoke the theme of the Final Judgement that follows the Resurrection, but in this case God is standing. Possibly, to evoke the Eucharist, as the priest is standing and elevates the sacrifice of his Son. Despite the figure of the Father seems very large, it is in fact not bigger than that of the Son, it is only a game of proportions.
In previous representations of the Trinity the background was always golden or heavens-like, in this case it was the first time it was located in an architectural space, which is an earthly place, fruit of human activity. The illusionistic power of the vault in the background is known to have impressed those who first saw the work. It seems to be looking at an actual chapel as Vasari stated.
The space is bordered by two pilasters with Corinthian capitals that support an entablature under which there are two ornamental medallions; two Ionic columns and a triumphal arch give access to the imaginary chapel. The depiction of the architecture follows the of perspective, cleverly used to create, through the depiction of the barrel vault and the other two columns on the chapel background, an illusionistic effect of depth. The lacunar ceiling is decorated with rosettes (now barely visible) alternately painted in shades of red and blue. The whole space is rather moderate in its proportions and at its center is the Crucifix. It is on the whole easy to see how Masaccio was inspired by Brunelleschi's architecture, probably by the Barbadori's Chapel in Santa Felicita.
The architectural frame hosts the Trinity in a pyramidal structure. On the background there is a platform on which God the Father is standing, he is wearing a red tunicle and a blue cloak he is holding the cross on which his Son is crucified. The Father's halo is quite large and makes him appear larger than he is. The Son is quite pale and his position stresses the weight of the dead body on the cross. The transcendence of these two figures exempts them from the rules of perspective. The Trinity is completed with the dove of the Holy Spirit who is in between the Father and the Son. On a lower level, closer to the spectator there are Saint John and the Virgin, the first is in sorrow, while Mary looks at the spectator with a sense of sever impassability and invites us to contemplate the extreme sacrifice of his Son.
Under them are two kneeling figures, probably those who commissioned the work. The detail of the portraits is incredibly high and it is a testimony of Masaccio's great skills.
Under this is the sarcophagus with a skeleton: a Memento Mori: what I am you will be too.
Masaccio becomes a "theologian" with this work, he enters the divine mystery of God. The first impression of the work might be the rational and humanistic, whereas it is much more. Not too many colours were used during the execution of this work, in order to exalt the scene itself.
Unfortunately many tend to define Renaissance works as theologically dull or "too nice" or even (and this is very popular) human-centred, clearly impossible in the Quattrocento, but nonetheless a theory proposed by too many (bad) history books.
The work is rich of iconographic and theological meanings that Masaccio surely discussed with the commissioner. It is not clear what the vaulted space signifies: a chapel? a tomb? the Golgotha? Heaven?
God the Father stands on what might be a great tabernacle of David. Probably it is a combination of a funerary monument and a representation of the Trinity: the work must be read vertically, from the bottom as an ascension to the eternal salvation. First we have the open sarcophagus with the skeleton to remind us of the shortness and uncertainty of the earthly life, then we have the commissioners and the human dimension, followed by the Virgin and John in the role of intercession and then the sacrifice of Christ and the salvation in the Father, through the Holy Spirit. Surely there might have been an altar for chantry masses. Last, but not least, it is important to notice that the work is located in a Dominican church and that the Resurrection is very important to Dominican theology: Christ is dead but he is also risen: our death will have the same solution.