distinction with a difference

In an “ontological fantasy,” characters from “our” niche interact with sentient beings from other niches, as in Shakespeare’s The Tempest and Tolkien’s The Lord of the Rings. The reader is not at liberty to doubt the existence of trolls, orcs, and elves, even if a character within the fiction does. Often the interaction borders on the sacred, as in Hamlet’s encounter with his father’s ghost. Walter M. Miller Jr., in a passage from A Canticle for Leibowitz, makes a clear distinction between ontological and epistemological fantasy. Dr. Cors and Abbot Zerchi are debating the merits of euthanasia. The skeptical doctor speaks,

“If I thought I had such a thing as a soul, and that there was an angry God in Heaven, I might agree with you.”
Abbot Zerchi smiled thinly. “You don’t have a soul, Doctor. You are a soul. You have a body temporarily.” (W.M. Miller 242)

Given leisure from hagiography, the abbot might enjoy an ontological fantasy. Dr. Cors might read an epistemological fantasy, though he would likely prefer psychological realism.
—David M. Miller, “Mommy Fortuna’s Ontological Plenum: The Fantasy of Plenitude”, in Contours of the Fantastic: Selected Essays from the Eighth International Conference on the Fantastic in the Arts, edited by Michele K. Langford, Greenwood Press, 1990, pp. 208-209