The medieval conception of dreams differs significantly from ours: dreaming was not the psychic activity of an individual, but his immediate getting in contact with the powers of the beyond, either positive or negative, during his sleep. Hence the distinction between “true” dreams (of divine origin) and “false” dreams (diabolic illusions) and the systematic suspicion towards dreams. Like miracles, dreams made it possible to legitimate any institution or any innovation. They also made it possible to discover a specific form of subjectivity: that of the Christian subject. His iconography is greatly inspired by biblical dreams and characterized by the juxtaposition in a same image of the dreamer's figure and dream's object. No “autobiographic” image of dream is to be found before Dürer’s famous watercolor. A good many medieval images show however that painters were also interested in expressing the dreamer's subjective experience.