[The essay from which this excerpt is taken was originally presented as a lecture at the Eaton Conference on Science Fiction and Fantasy at the University of California, Riverside, in 1980.]

[In trying to determine the relationship between fantasy and science fiction, fantasy] honors the emotive side of the self, what I call the nighttime perspective. The extreme alternative is literature devoted to the exercise of the daytime powers of the intellect. Here my quintessential specimen is John Campbell's "Who Goes There?" The dramatic situation is much like that of [The Invasion of the] Body Snatchers, but the art teaches us a very different response. Again, an alien thing capable of swallowing humans and making perfect replicas has gotten loose. Some members of the population have already been processed; some have not. How can the thing be stopped?

The scientists of "Who Goes There?" respond, not with screams (or...