Though we discussed all the issues involved in the duality inherent in our culture and language, I don't think we really discussed the issue of duality itself as Ursula Le Guin portrays it in The Left Hand of Darkness. It is true that our fixation with the opposites of male and female make interpreting the world of Gethen difficult; we can't quite comprehend the idea of androgynous humans. But this doesn't mean our refusal to let go of this way of thinking is necessarily bad. We think of many important ideas in this way, not just gender--light/dark, good/evil, black/white, right/wrong, nature/civilization. The point is, however, that in any duality, neither half is better or more important than the other. As Estraven says, " 'It's queer that daylight's not enough. We need the shadows, in order to walk.' " (267) Genly Ai of course points out the yin yang symbol to Estraven, something we as a society often reference.
If we consider this further, however, there is another reason thinking in dualities is not inherently a bad thing. Though we specifically name the two ends of the spectrum, we also recognize the area between as having possibility--the "gray" area, both a combination of black and white and between them. Obviously, we have the middle word for the black/white duality, but what's the middle word for the right/wrong or good/evil duality? We don't have one (that I know of--feel free to correct me). We do understand the concept this middle word would describe, however, because there are so many instances in life that cannot be placed at either end of the spectrum. I think Le Guin is in part identifying one middle concept that we haven't really considered, which is why it is so difficult for us to comprehend. Maybe over time there will be a need for a pronoun to describe an "it" in a non-degrading way, but in the novel androgyny is used at least partially to show how our idealistic dual way of thinking applies to the real world. As she says in the introduction, Le Guin is "merely observing" and "describing" (5th pg of intro) the world as it currently exists.
On a different train of thought, Le Guin also interestingly critiques nationalism, patriotism, and war. The Gethenians have no word for war, probably a result from rather than a cause behind the fact they have never had a war--just small competitions, though sometimes equally fatal. On the subject of patriotism, Estraven asks, "[W]hat is the sense of giving a boundary to all that, of giving it a name and ceasing to love where the name ceases to apply? What is love of one's country; is it hate of one's uncountry?" (211) Of course, it is in order to change this view, in order to bring the nation of Karhide together that Tibe wants to create war with Orgoreyn, though this is difficult without an actual word to describe his intent. "He was after something surer, the sure, quick, and lasting way to make people into a nation: war. . . . The only other means of mobilizing people rapidly and entirely is with a new religion; none was handy; he would make do with war." (103) (Is this also a critique of religion--or at least new religion, which is simply a cult? Must ponder later.) War obviously does create nationalism--Americans never feel more American than when they are banded together against some foreign enemy. I'm not sure, however, why war and religion are the only two options for Tibe. Why he wants war is only more unclear with the interesting observation, "If civilization has an opposite, it is war. Of those two things, you have either one, or the other. Not both." (102) It would follow, then, that if the country waged war, it would be nationalistic but no longer actually a country, just a fighting body. Perhaps it is through the idea that in war we regress to more animalistic, aggressive ways of viewing our enemy. Even more interesting is that Le Guin has provided us with another duality to consider: war and civilization. In this case, is there still a middle ground, as in the other dualities? Once again, interestingly, it seems the Gethenians have the answer: they have both civilization and conflict, but their conflicts are limited to small numbers of people, and most often people within a country, not between countries.
This is an impressively relevant quote, and I think one that highlights the point of LeGuin's entire novel. She has put us into a situation in which the typical dualities no longer apply, and the discomfort we feel is the same that Estraven and Genly experience when the entire world is bright, up on the ice.
I believe someone said this in class, better than I: As humans, we require definition to function. We cannot deal with the overwhelming complexity of the world without breaking it into pieces and defining each piece. In doing so, however, we lose a large amount of information. Trying to split the entirety of human sexuality into explicit "Male" and "Female" roles is much like trying to split all fruit into either bananas or oranges - it's not possible, but as humans, we try and do it anyway.
I know that this introduction didn't relate to your point, but bear with me. I think it is interesting that you say that there is no normative implication in any of these dualities. You say that good and evil are both necessary, or that light and dark are both necessary, but this does not imply that both are normatively equal. Clearly, in common speech, good is better than evil, light is better than dark, etc. I can see the necessity for both these distinctions: Light from dark allows us to see, good from evil allows us to determine a correct course of action.
It is interesting, then, that you compare light/dark and good/evil to male/female, which seems to me to be a much less intrinsically necessary distinction than it is often portrayed to be. Evolutionarily, it is important to know who you can mate with to naturally produce viable offspring, but in a culture in which birth is no longer the primary purpose of most committed unions, the distinction loses some of its importance. I think that Leguin's purpose with the repeated comments by the characters is to make us consider that "gray" area, as you say. In my personal opinion, that "gray" area is usually defined, in the case of gender and sexuality, by its two extremes. However, I think that the gray area need not be defined this way, and so it is there that Leguin's metaphor breaks down.
Obviously, we have the middle word for the black/white duality, but what’s the middle word for the right/wrong or good/evil duality?
There's a great passage in The Crying of Lot 49 in which Pynchon ponders the power of "excluded middles," referring to them as "bad shit." That which is excluded, for him, is in fact the most important term...