In 1933, Wells wrote an introduction to a collection of his writings called The Scientific Romances of H. G. Wells, in which he elaborated a principle that he said he followed when writing The Time Machine. The principle has since come to be called Wells’s Law. Wells believed that a work of speculative fiction should contain no more than one extraordinary concept—such as time travel, alien invasion, invisibility, human-animal hybrids—couched in an otherwise normal human world. The author’s task is to extrapolate the implications for the real world (and for a fictional protagonist) of this one impossible thing. Thus, in The Time Machine, the single remarkable thing is the machine itself, and everything else in the story is speculation on what such a machine might reveal.

Wells explains: “‘How would you feel and what might not happen to you,’ is the typical question, if for instance pigs could fly and one came rocketing over a hedge at you […] But no one would think twice about the answer if hedges and houses also began to fly” (Wells, H. G. The Scientific Romances of H. G. Wells. V. Gollancz Ltd., 1935, viii.) Too much impossibility at once makes readers give up in frustration; they withdraw their willing suspension of disbelief, and the story fails.