This important contribution to the study of science fiction explores the origins of the basic literary traditions of the genre. Thematic, rather than chronological, organization sets this work apart from previous analyses. The entire range of literary invention within science fiction is explored from its earliest beginnings through the past hundred years of serious development. Emphasis is on enabling the reader to perceive the evolution of science fiction as an organic whole, rather than a mere accumulation of works linked solely by popular publishing trends.