Suppose, in the far future, an isolated planet somewhere in the distant reaches of the galaxy has been colonised by humans and then left alone. That relatively small pocket of humanity, forced to adapt over time to a hostile environment, may well evolve into a different kind of humanity.

The prevailing low atmospheric temperature might encourage a society that takes extremes of winter in its stride. Other factors may encourage the species to evolve into a form of hermaphrodism, each person being normally neuter, changing randomly to male or female for procreation.

Such is the society that accepts the Ekumen Envoy, Genly Ai, when he arrives on the planet Gethen to assess its suitability to join the galactic empire. Almost at once the envoy's efforts are thwarted, when the kingdom's representative, with whom Ai has been carefully negotiating, is denounced as a traitor.

Ursula LeGuin's The Left Hand of Darkness is Genly Ai's report of his attempts to establish friendly communications with the different societies on the planet. We see nearly everything that happens from his point of view, and since he is, in effect, a human visitor on an alien planet, we see the planet's peculiarities through his eyes.

The Left Hand of Darkness contains several science- fictional ideas that have, since its first publication in 1969, become classics; the most notable being the 'ansible' -- a device to enable instantaneous communication across relativistic distances. Another is the single-sex society, in which members are neither male nor female except at those times when they are ready to reproduce.

LeGuin does a superb job extrapolating the implications of this radically different humanity, even inventing a detailed mythological legacy.

As lone ambassador to the planet Gethen (meaning 'winter') the envoy Ai appears vulnerable, and though the reasons for his unaccompanied visit are convincingly explained, his vulnerability drives the plot. Whereas the beginning of the novel shows the political consequences of Genly Ai's efforts, the latter half is a more personal story following the main characters when they find themselves up against the planet's inhospitable environment.

LeGuin's achievement is not just to give us convincing SF ideas, but also to have us believing in the overall social structure and the motivations of the individuals. This is world-building of a rare capacity, complete with an appendix should we wish to research the background.

The Left Hand of Darkness is a richly textured novel, showing us human societies so different from our own that they can be considered truly alien.

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