The Left Hand of Darkness

I have just finished the left hand of darkness by Ursula LeGuin, and I am supposed to write an essay about it.

Estraven says: " Light is the left hand of darkness / and darkness the right hand of / light. The two are one, life and death, / lying together like lovers in / kemmer, like hans joined / together, like the end and the way. "

What does this obviously crucial quoate mean? Is it a tribute to "the whole", that the gethenian human are? A whole of both sexes? Isn't this whole very important in the book? A whole uniting all opposites - loyality and betrayal, shadow and light, man and woman. Is this the books mission? To show how nothing is opposites - but a whole?

Then what is the meaning of the travel on the ice, where the shadows disappear, and Estraven and Ai aren't able to see anything? - possibly a whole?

Am I right, or do you have any other interesting angels and points? I am curious!

Thank you all in advance!

Regards, Maria