You Can't Have One without the Other.
In The Left Hand of Darkness, Ursula K. Le Guin uses the duality of light and darkness as one of her main tools to show that each one is equally important. A lot of the things that Le Guin talks about in her book have some type of opposite, which is extremely similar to duality. Her use of light and dark is significant because it shows her audience how two completely different things are very much alike. Le Guin takes light and darkness to another level that is incredibly different from the perception that society has of the two. Le Guin uses light and darkness as one of the tools of duality to show that they are each needed in order to form the perfect union.
The Left Hand of Darkness is set in Gethen, a tremendously cold planet. Here in Gethen, gender differs greatly than it does on earth. Gethians are neither looked upon as males or females when first encountered. The gender of one depends upon which role they take while in kemmer. Kemmer is a part their sexual cycle which generally lasts for 26 to 28 days. After two partners who are both in kemmer interact with each other, their sexuality will come into play depending how their hormones generate. In Gethen they do not see each other as men or women. To Gethians earths entire pattern of social-sexual interaction is nonexistent. A man by the name of Genli Ai comes to this planet, Gethen, from earth trying to persuade the Gethians to join a planetary union. After failing to do so, he begins his journey to Orgoreyn, Karhides rival nation and tries to convince them. While on his journey Genli Ai runs into a man by the name of Estraven who is in exile at Karhide. Throughout all of their struggles and differences, they finally come together and end up relying, trusting and loving one another.
The main idea of duality that Le Guin uses to get her message across to the reader is the difference between Genli Ai and Estraven.