As Kant was writing about the possibility of spiritual apparitions, the emerging medium of the phantasmagoria used hidden magic lanterns to startle audiences with ghostly projections. Andriopoulos juxtaposes the philosophical arguments of German idealism with contemporaneous occultism and ghost shows. In close readings of Kant, Hegel, and Schopenhauer, he traces the diverging modes in which these authors appropriated figures of optical media and spiritualist notions.
The term "appearance" has been used in different apparitions within a wide range of contexts and experiences. And its use has been different with respect to Marian apparitions and visions of Jesus Christ.
In some apparitions such as Our Lady of Lourdes or Our Lady of Fatima an actual vision is reported, fully resembling that of a person being present. In some of these reports the viewers (at times children) do not initially report that they saw the Virgin Mary, but that they saw "a Lady" (often but not always dressed in white) and had a conversation with her. In these cases the viewers report experiences that resemble the visual and verbal interaction with a person present at the site of the apparition. In most cases, there are no clear indications as to the auditory nature of the experience, i.e. whether the viewers heard the voices via airwaves or an "interior" or subjective sense of communication. Yet, the 1973 messages of Our Lady of Akita, which were approved at the Congregation for the Doctrine of the Faith in 1988 by Cardinal Joseph Ratzinger (later Pope Benedict XVI) are due to Sister Agnes Katsuko Sasagawa who had been totally deaf before 1973 (and remained deaf until 1982 when she was cured during Sunday Mass as foretold in her messages), suggesting means of communication other than airwaves.
In some apparitions just an image is reported, often with no verbal interaction, and no conversation. An example is the reported apparitions at Our Lady of Assiut in which many people reported a bright image atop a building, accompanied by photographs of the image. The photographs at times suggest the silhouette of a statue of the Virgin Mary but the images are usually subject to varying interpretations, and critics suggest that they may just be due to various visual effects of unknown origin. However, such image-like appearances are hardly ever reported for visions of Jesus and Mary. In most cases these involve some form of reported communication.