(εἰκών , image; κλάζειν, to break), is a name for the struggle in the Christian Church in the Middle Ages., which, as its name indicates, had for its object the destruction of all images used for worship in the churches. From the age of Constantine the reverence for pictures and images constantly increased, as they were supposed to possess a certain sanctity or miraculous power; and at so early an age as that of Augustine we hear him confess that many had fallen into the superstition of adoring pictures rather than the Deity. But the Iconoclastic controversy assumed a more serious aspect in the 8th century, when the emperor Leo III, the Isaurian (717741), who, previous to his accession to the throne, had associated much with Jews and Mohammedans, on talking the side of the Iconoclasts in the tenth year of his reign, issued an edict against the use of images in churches. He was influenced, no doubt, by a desire to draw into the Christian Church the Mohammedans and Jews, who, aside from their simple theistic faith, were debarred from joining the Christians by an aversion to the use of images. But the people-who felt that "it swept away from their churches objects hallowed by devotion, and supposed to be endowed with miraculous agency; objects of hope and fear, of gratitude and immemorial veneration" rose up in masses against the edict, and violent disturbances, especially at Constantinople, where the patriarch himself sided with them, were of daily occurrence. The superior power of the government, however, soon made itself felt, the pictures were destroyed, the insurrectionists slain or banished, and order restored, after a fearful massacre.
Yet, notwithstanding all the penalties which, by order of Leo, were inflicted on the opponents of Iconoclasm, champions in favor of the use of images in churches rose up. Among them was the great John of Damascus (q.v.), who, after adducing the ordinary arguments for images with greater elegance and ingenuity than any other writer of his day, went forth in bitter invectives against the Iconoclasts as enemies of Christ, the Virgin, and the saints. "Pictures are standing memorials of triumph over the devil; whosoever destroys them is a friend of the devil, a Manichean, and a Docetist." The pope himself, Gregory III, put all the opposers of images under ban; but, despite this and other efforts on his part, Leo's successor, Constantinus Copronymus, went even further than Leo. Having obtained the condemnation of image worship in the Synod of Constantinople in A.D. 754, he enforced it against the clergy and the most noted of the monks. Many monks, who, together with the patriarchs of Alexandria, Antioch, and Jerusalem, were in favor of the images, and were unwilling to subscribe to the decrees of the council, were cruelly persecuted. The emperor Leo IV also enforced this law; but his widow, Irene, one of the basest of women, used the tendency of the people in favor of image worship to enable her to ascend the throne. With the aid of the newly elected patriarch of Constantinople, Terasios, she called a synod at Nicaea in 787, wherein the adoration of images by prostration, kissing, and incensing was reestablished. Matters remained in this state during the reigns of the emperors Nicephorus and Michael (802- 813), although there still were Iconoclasts to be found. But as, during the strife, the adoration of images had passed into the grossest idolatry, Leo V (813-821) caused it to be abolished by the Synod of Constantinople, and punished those who persisted in it (mostly monks, with Theodoros Studita at their head). Michael II (821-824), who overthrew Leo, tolerated the worship of images without thereby satisfying the image worshippers; but Theophilus, his son (829-842), on his sole accession to the government, renewed all the edicts against them. After his death, his widow restored image-worship in 842, and instituted the festival of the Orthodoxy, which is yet kept by the Greek Church in remembrance of this restoration (see Buddaeus, De festo orthodoxo, Jena, 1726).
The Greek Christians have since retained images in their churches, but without worshipping them. The Latins also decided that the images should be retained, but not worshipped; while the French Church declared most positively against image-worship in the Synod of Gentiliacum in 767, and in 790 Charlemagne presented to the Council of Nicaea a memorial, De inmpio imne qunzcum cultu (Libri Carolini). Thereupon images were allowed to be retained for purposes of education only. At the Synod of Frankfort in 794, Charlemagne, with the assent of the English Church, caused image-worship to be condemned. After the 9th century the popes were gradually more inclined towards image-worship, and it soon became general throughout the West. The Roman Catholic Church continued to favor the practice, an-d the Council of Trent decided formally in its twenty-fifth session that the images of Christ, of the holy Virgin, and of other saints are to be placed in churches; that they ought to receive due veneration, not because they have any divinity or virtue in them, but because honor is thus reflected upon those whom they represent; so that the people, by kissing the images, bowing to them, etc., pray to Christ and honor the saints whom the images represent. This image-worship led to pilgrimages to the shrines of saints great in repute for their power. The Greek Church admits only the painted and raised images, not carved figures, like the Church of Rome. All the Christian sects in the East are given to image-worship with the exception of the Nestorians, the Christians of St. Thomas, and the Russian Roskolniki. The German Reformers, although opposing image-worship, held somewhat different opinions on the subject: thus Luther tolerated images as an ornament, and also as edifying mementoes, and condemned the destruction of the images and the altars at Wittenberg in 1522. The Swiss Reformers opposed images in any shape or for any purpose, and had them taken out of all the churches-often with great violence, as in the Netherlands. They are not even now tolerated in the Reformed Church, nor in the particular denominations that have sprung from it. Mohammedanism proscribes image-worship; it even forbids the reproduction of the image of any living being, though it be not for the purpose of worshipping it. See Wessenberg, Die christlichen Bilder, ein Beforderungs mittel d. christ. Sinnes (Constanz, 1827, 2 vols.); Schlosser, Gesch. der Bilderstü rmenden Kaiser (Frankf. ad. M. 1812); Marx, Der Bilderstreit der Byzantinischen Kaiser (Trier, 1839); Ketzer Lex. 2, 287; Milman's Gibbon, Decline and Fall of Romans Emp. 5, 10 sq.; Milman, Latin Christianity, 2, 293 sq.; Pierer, Universal Lexikon, s.v. Bilder; Bingham, Orig. Eccles. book 8, ch. 8; Butler, Eccles. Hist. (Phila. 1868), 1, 860 sq. Ranke, History of the Popes, 1, 19-25. (See IMAGE-WORSHIP). (J. H.W.)