Today we take the word icon to mean a sign, or we equate it with portraits of Christ and the saints. In The Sensual Icon, Bissera Pentcheva demonstrates how icons originally manifested the presence of the Holy Spirit in matter. Christ was the ideal icon, emerging through the Incarnation; so, too, were the bodies of the stylites (column-saints) penetrated by the divine pneuma (breath or spirit), or the Eucharist, or the Justinianic space of Hagia Sophia filled with the reverberations of chants and the smoke of incense. Iconoclasm (726-843) challenged these Spirit-centered definitions of the icon, eventually restricting the word to mean only the lifeless imprint (typos) of Christs visual characteristics on matter. By the tenth century, mixed-media relief icons in gold, repousse, enamel, and filigree offered a new paradigm. The suns rays or flickering candlelight, stirred by drafts of air and human breath, animated the rich surfaces of these objects; changing shadows endowed their...