Caroline Walker Bynum writes:
The events and beliefs of the Middle Ages that have appeared unusual to later centuries have always attracted attention of two rather different sorts. One tendency has been to explain them away. For example, sophisticated and thoughtful about many religious phenomena though he was, in The Varieties of Religious Experience William James tended to reduce the mystical experiences of medieval women, especially when accompanied by bodily rigidity, swelling or trances, to psychological aberrations. Catholic scholars such as Herbert Thurston also attempted to explain a number of supposed miraculous occurrences such as stigmata or the incorruptibility of bodies after death as natural or artificially induced effects. For at least 150 years, chemists and biologists have delighted in pointing out that a red fungus known as micrococcus prodigiosus could account for alleged miracles of bleeding communion hosts. Art historians have occasionally suggested that new objects such as hanging lamps in the shape of doves or brightly painted statues might have caused visionary experiences when worshippers in dusty and smoke-filled churches mistook them for apparitions.