Reading Lewis's essays on art, atmosphere, and Otherness in works of fiction, John W. Campbell's story "Who Goes There?" (Cue words: Antarctica, scientists, shapechanging alien) came into my mind as an example of one of Lewis's point. Sometimes the science part of Science Fiction is unimportant - there are only the trappings of science, but the same story could have been managed in another form.
Certainly true. In the above, shapeshifting by any means would have been sufficient. No need for aliens. I wonder how often that is the case with Science Fiction, that it is really more speculative fiction with a little science thrown in. I have no idea whether it was more common in the old days or more common now.