Art therapists today help their patients cope with anxiety, addiction, illness, or pain. Therapists might encourage clients to explore their emotions by drawing, for example, or to reflect on a difficult experience through painting. Art is used to help people express themselves and explore their emotions. In past centuries, however, art therapy took a substantially different form. Maybe it’s time to bring this practice of the past into the present—as a way to move into the future. The Isenheim Altarpiece is a 16th century sculpted and painted work housed in an old convent-turned-museum in the medieval city of Colmar, France—a city with wood-framed houses and winding footpaths that appear to have changed little in 500 years. Altarpieces have long been used to decorate churches and to tell stories, but the Isenheim Altarpiece offered an additional therapeutic function. The religious order that cared for the sick, the Antonites, “prescribed” viewing the altarpiece to those in their ho...