Lion-headed door knocker (diameter 17.4 inches) circa 11th century. Photograph: Gary Wayne Gilbert

As anyone who has traveled even a little in the Islamic world will have noticed, a door is not just a door. More often than not, doors are only the outward, visible sign of a residence—highlighted gateways to the inner courtyard and the intimate, sacred domain of the family, which necessarily remains hidden from the everyday business of the outer, social world. Doors, then, are the architectural equivalent of the veil, which blocks the profane glance but is transparent to the purified vision of the heart. For wherever we encounter doors in Islamic civilization, they always represent another threshold, the liminal space between the outer, manifest realm of creation and its inner, spiritual reality and source.

The metaphysical “keys” to that doorway, to realizing our essential nature as reflection of the divine, are tellingly summarized, in their most abstract terms, in the Islamic phrases—repeated many times each day in prayer—that are carefully inscribed around the door knocker above: “In the Name of God, the All-Loving, the All-Compassionate” (ascending on the left); and (descending on the right) the profession of faith: “I witness that there is no God but God, and that Muhammad is the Messenger of God.”

The first phrase summarizes the process of divine “Cosmo­philia,” that all-encompassing divine Love that brings the cosmos into being at every instant; while the second phrase is meant to remind us of the all-encompassing divine Compassion that has provided all humanity, through the many prophets and messengers, with those revealed pathways leading to the full recognition and active realization of that divine Love. Both keys are beautifully summed up in the memorable divine Saying: “I was a hidden Treasure, and I loved to be known; so I created creation—and humanity—so that I might be known.”

Practically speaking, what first awakens in us that realization of the divine Beauty is above all its expression in the world of nature, a realm constantly evoked in the familiar Qur’anic symbolism of the wonders of the heavens; the water of divine life; the fountains, greenery, flowers, breezes, and perfumes of Paradise; the life-sustaining blessings of the animal world; and, above all, the constant presence of the “Friends of God,” or saints. Thus, a key spiritual function of all Islamic arts is to evoke each soul’s awareness of the divine Presence, of the divine Names that shape and inform every moment of our existence and perception.

That awakening to the divine Beauty and presence marks only the beginning of the spiritual journey. The next stage—the natural human response to that universal Beauty and the transforming love it engenders—is the ongoing challenge of ethical and spiritual action and creativity. Each human being is challenged to discover how to mirror, express, and communicate that beauty and awareness in life, from the mundane requirements of social existence to the heights of spiritual devotion. In the Qur’an, that call to the sacralization of all existence is summed up in the central spiritual virtue of ihsān, a pregnantly untranslatable term that means the active, spiritually effective realization of what is simultaneously both good and beautiful, in every area of life.

Over more than a millennium, and from Spain to China, this insistence on ihsān, on the “beautiful-sacralization” of all our existence, was creatively expressed not just in “fine arts” and luxury goods, but in the utilitarian crafts and everyday articles of life. This particular door knocker strikingly underlines the lesson. For it comes not from what we today think of as an “Islamic” land, but from feuding Norman kingdoms of 11th- or 12th-century Italy and Sicily, from cities in which—despite ongoing Crusades and cycles of violent upheaval—Muslims and Christians managed to forge a remarkably cosmopolitan, trans-Mediterranean civilization whose creations survive, not just in works of beauty but in words, foods, architecture, philosophy, science, and medicine that we take for granted.

James Morris, a professor of theology at Boston College, is the author of The Reflective Heart: Discovering Spiritual Intelligence in the Meccan Illumi­na­tions (2005). His essay is adapted from remarks prepared for the audio tour of Cosmophilia, an exhibition at the McMullen Museum through 2006.