As illustrated in the above painting, the holy stigmata is a seriously cosmic affair. We see Saint Francis of Assisi (1181 - 1226) on the slopes of Italy's Mount La Verna, visited by a fiery vision of a crucified Christ -- the flames twisting into the form of seraph wings. According to Catholic lore, so intense was this mystic experience that it inflicted the wounds of crucifixion on Francis' hands and feet.
Images such as these would indicate that heavenly lasers pierce the flesh of a stigmatic individual, but bleaker, skeptical interpretations tend to lean more on self-inflicted harm induced by starvation (Francis himself was in the midst of a lengthy fast), post-traumatic stress or a dissociative disorder.
Another frequently-explored possibility is that stigmata (which vary from topical lesions to deeper apertures) might be psychogenic in nature, which is to say they are physical, psychosomatic maladies stemming from mental or emotional stress [source: Margnelli]. It's a quite reasonable hypothesis if you buy into studies on hypnosis-induced burns and allergic reactions. How might the altered states of spiritual ecstasy and deep meditative prayer affect the mind/body connection?
But there's a third possibility, at least concerning the stigmata of Saint Francis: Might his original, trend-setting stigmata have manifested as the symptom of infectious disease?
Francis suffered from various ailments, including a painful, blinding eye infection that the historian Dr. Edward Frederick Hartung identified as trachoma. But the late Dr. Hartung also believed that the saint's death, just two years after the alleged 1224 visitation on Mount La Verna, was likely due to malignant malaria. Though rarely encountered with today's treatments, one complication of the infection is the purplish hemorrhage of blood through the skin, known as purpura. What's more, purpura usually distribute symmetrically on the hands and feet [source: Time]. Is it possible that the saint's supernatural wounds were mere hemorrhages?
Or perhaps, as suggested by Joanne Schatzlein and Daniel P. Sulmasy, Francis suffered his stigmata as a symptom of leprosy. Their 1987 paper "The Diagnosis of St. Francis: Evidence for Leprosy" explores the possibility that the wounds were either the irregular skin lesions caused by borderline leprosy or the solitary, often-asymmetrical lesions caused by tuberculoid leprosy.
Naturally, we can never know for certain where Francis' stigmata came from, but perhaps they're all different shades of the same thing. Presumably, the creator God that would have sent the seraph would have also created the protozoans responsible for malaria and the bacteria responsible for leprosy. Francis seems to suggest as much himself in "Little Flowers of St. Francis."
Worldly or otherworldly, the stigmatic wounds inspired piety in Francis and centuries of religious tradition have cemented their place amid Catholosism's more sanguine motifs.