Beyond the fact that it was originally published in a science fiction magazine, I am certain that ["Waldo"] is a science fiction story rather than a fantasy story, but I am very far from certain that I can satisfactorily explain why.

The basic elements of "Waldo" are four: a Pennsylvania hex doctor who may be well over a hundred years old and whose magic actually works; "deKalb power receptors" that have suddenly ceased to operate properly though nothing seems to be wrong with them; a rising incidence of general myasthenia—abnormal muscular weakness and fatigue— in the population; and Waldo, an engineering genius and paranoid misanthrope afflicted by myasthenia gravis who lives in a satellite home popularly known as "Wheelchair." Heinlein has managed to tie this all together into a fascinating whole.

The deKalbs are failing, and their proprietors, North American Power-Air Co., are worried...