What is the theme in The Left Hand of Darkness by Ursula K. Le Guin?

Sex Roles are a recurring idea in the story. When asked by his Gethenian friend how women on Earth are different from men, Genly Ai responds, "It's extremely hard to separate the innate differences from the learned ones. Even where women participate equally with men in the society, they still do all of the childbearing, and so most of the child-rearing…." After mulling over how little the differences are between men and women, yet how different their roles in society, he concludes, "In a sense, women are more alien to me than you are. With you I share one sex, anyhow…."

When asked by his Gethenian friend how women on Earth are different from men, Genly Ai responds, "It's extremely hard to separate the innate differences from the learned ones. Even where women participate equally with men in the society, they still do all of the childbearing, and so most of the child-rearing…." After mulling over how little the differences are between men and women, yet how different their roles in society, he concludes, "In a sense, women are more alien to me than you are. With you I share one sex, anyhow…."