Given the iconoclastic half-century that has passed, it can never be amiss to remind ourselves of why the Catholic Church of East and West has always produced, loved, venerated, and defended “icons” or holy images of Christ, His Mother, and all the saints. Although in what follows I will be speaking primarily of icons in the usual sense of the term, the theological principles definitely apply to stained glass, relief carvings, sculptures or statues—in short, any art that seeks to bring the holy ones into our midst or, more properly, to bring us into contact with their glory.
In response to heretics who were rejecting and destroying holy images (the iconoclasts), the seventh Ecumenical Council of the Catholic Church, called the Second Council of Nicaea (787), unambiguously affirmed the constant teaching and tradition of the Church:
We declare that we preserve intact all the written and unwritten traditions of the Church which have been entrusted to us. One of these traditions consists in the production of representational artwork, which accords with the history of the preaching of the Gospel. For it confirms that the Incarnation of the Word of God was real and not imaginary . . .The Council continued:
We, therefore, following the royal pathway and the divinely inspired authority of our Holy Fathers and the traditions of the Catholic Church (for, as we all know, the Holy Spirit dwells in her), define with all certitude and accuracy that, like the figure of the precious and life-giving Cross, so also, venerable and holy images of our Lord God and Savior Jesus Christ, of our spotless Lady, the Mother of God, of the honorable angels, of all saints and of all the just, whether painted or made of mosaic or another suitable material, are to be set forth in the holy churches of God, on the sacred vessels, on the vestments, on walls and panels, in houses, and on streets. For the more frequently they are seen in artistic representation, the more readily men are lifted up to the memory of their prototypes and to longing after them; and to these should be given due greeting and honorable reverence, not indeed that adoration (latreia) which pertains to the divine nature alone, but incense and candles may be offered to these, as to the figure of the precious and life-giving Cross, the Book of the Gospels, and other holy objects, according to ancient and pious custom. For the honor that is paid to the image passes on to what the image represents, and he who reveres the image reveres in it the subject represented.Much later on, in response to a new wave of iconoclasm fomented by the Protestants who accused Catholics of “idol worship” in violation of the first Commandment, the Council of Trent had this to say:
The images of Christ, of the Virgin Mother of God, and of other saints are to be kept and preserved, in places of worship especially, and to them due honor and veneration is to be given, not because it is believed that there is in them anything divine or any power for which they are revered, nor in the sense that something is sought from them or that a blind trust is put in images as once was done by the gentiles who placed their hope in idols, but because the honor that is shown to them is referred to the original subjects that they represent. Thus, through these images that we kiss and before which we kneel and uncover our heads, we are adoring Christ and venerating the saints whose likeness these images bear.The Fathers of Trent mention that this is the teaching of the Councils, especially the Second Council of Nicaea.
St. Thomas says this about the Christ icon in the Summa:
No reverence is to be shown to Christ’s image, insofar as it is a thing (for instance, carved or painted wood); because reverence is not due except to a rational creature. It follows therefore that reverence should be shown to it, only insofar as it is an image. Consequently, the same reverence should be shown to Christ’s image as to Christ Himself. Since, therefore, Christ is adored with latria, it follows that His image should be adored with the adoration of latria.
1. They are a means of honoring God, his saints, and the holy angels. As St. Basil the Great said, in a line often quoted by Damascene and invoked by Nicaea II: “The honor that is given to the icon passes on to its prototype [i.e., original].”
2. They serve to instruct us in the Christian Faith. They are like books: “What the book is to the literate, icons are to the illiterate, and what speech is to hearing, that the icon is to sight.” (Allow me to note that all of us are, to some extent, illiterates, in the sense that we do not fully grasp what we read in the Bible, and need many ways of entering into the mystery of God.) Books and speech teach by words; icons teach by forms and colors. Damascene: “Icons are . . . the never-silent heralds of the honor that is due to holy persons. They teach those who see them with a soundless voice.”
3. They remind us of what we have learned. Like a book always lying open, they serve as a “concise memorial.” St. Gregory the Great: “The art of painting vividly brings the story to the mind.”
4. They lift us up to the prototypes; they are anagogical, leading us to the heavenly realm which is our final destiny. St. Dionysius: “By sensible images, we are led upward, as far as possible, to divine contemplations.” Cavarnos: “Icons lift our soul from the material to the spiritual realm, from a lower level of being, thought, and feeling, to a higher level.” Damascene has some beautiful things to say about this: “I enter into the place of therapy for souls, the church, choked by thoughts as by thorns. The blossom of the paintings attracts me to gaze at it, and as a meadow delights my sight and imperceptibly instills into my soul the glorification of God.” Later on, we read of the famous iconographer St. Andrei Rublev and his fellow artist Daniel: “On feast days when they did not work, they used to sit in front of the divine and venerable icons and look at them without distraction . . . They constantly elevated their spirits and their thoughts to the immaterial and divine light.” (This is the light that Rublev was able to transmit in his work.)
5. Icons powerfully incite us to virtue and to holiness, since they urge us to strive to imitate the prototypes—to copy their virtues and to avoid vices contrary to these. We are to become, as it were, living icons on which the divine Artist inscribes a holy image, beautiful to behold, full of form and color, so that we become a blessing for all who meet us.
6. The sixth purpose is our sanctification. Damascene teaches that icons of Christ and His Saints “are filled with the Holy Spirit”: during their life on earth, they were filled with the Spirit, and when they died, the grace of the Spirit remained in their souls, their bodies in the grave, and their icons. (This is why veneration of icons is connected with veneration of relics.) When we venerate an image of Christ in particular, we become partakers of His divine grace; the icon serves as a quasi-sacrament through which the life of our God is imparted to us.
7. Lastly, icons enhance the adornment of the church building. They set the house of God apart from common buildings and make it well suited for the divine liturgy that takes place within it. They make the church, in fact, an earthly image of the heavenly Jerusalem, where Christ and all His saints and angels rejoice in glory.
May Holy Mary and all the saints intercede for us with the Lord, that we may merit to be helped and saved by Him who lives and reigns, for ever and ever. Amen.
 Cited in CCC 1160.
 Council of Trent, Session XXV, December 1563.
 Summa theologiae, III, qu. 25, art. 3.
 As summarized in Cavarnos, Guide to Byzantine Iconography, 241–45.
 I say "quasi-sacrament" precisely because while the icon disposes us to receive the grace it signifies, it does not cause that grace ex opere operato, as a sacrament does. The icon is an occasion through which to beseech and receive grace, not a proper cause of the sanctification of the soul.
 Just in the opening days of April, three are commemorated: "April 1. At Constantinople, St. Macarius, Confessor, who under the Emperor Leo ended his life in exile for defending holy images. ... April 3. In the monastery of Medikion in Bithynia, St. Nicetas, Abbot, who suffered much under Leo the Armenian, for the veneration of holy images, and finally, as a confessor, died in peace near Constantinople. ... April 4. At Constantinople, St. Plato, monk, who strove with dauntless spirit for many years against the heretical breakers of holy images."