Arthur Machen's “The Inmost Light,” much like The Great God Pan, details the shocking effects of an experiment in human neurology. A certain Dr. Black labors to reconcile physiological with occult science, his goal being to “bridge over the gulf between the world of consciousness and the world of matter” (p. 182). “[F]rom some human being,” he explains, “there must be drawn that essence which men call the soul, and in its place … would enter in what the lips can hardly utter, what the mind cannot conceive without a horror more awful than the horror of death itself” (p. 182). Dr. Black here appears to affirm that a human “soul” exists independently from the human body, and thus that human identity cannot be fully explicated within a materialist framework.

Yet the story as a whole will not bear out this conclusion. It dwells obsessively on the horrific prospect of a human being conceived in utterly material terms. The doctor's work establishes that the “soul” is seated within the physiological reality of the brain; once extracted, moreover, it appears as a “splendid jewel” (p. 180) – exquisitely beautiful, but nonetheless most corporeal. The demonic force that then gains entry into the evacuated human body is not malevolent in any spiritual sense: it seems rather a representation of the grossly physical, animalistic potentialities of human beings, like the satyr-deity in The Great God Pan. Dr. Black's experimental subject becomes an abomination, the sight of which arouses violent symptoms – nausea, “cold sweat,” shortness of breath – in the spectator (p. 160).