Beyond the Wall of Sleep

A madman, Joe Slater, has fits during which he seems to be another person entirely. The narrator, a worker in the mental hospital in which Slater resides, had, during his college days, developed a device for transmitting thoughts. It didn't actually work, but he spruces it up and uses it regularly on Slater. Finally, as Slater is about to die, the device seems to work--it puts the narrator into communication with the being that occasionally possesses Slater, and he learns that all people are truly formless energy beings who are sometimes imprisoned in human form.

The idea is somewhat interesting, but the story really isn't.