“I expect it will turn out that sexual intercourse is possible between Gethenian double-sexed and Hainish-norm one-sexed human beings, though such intercourse will inevitably be sterile. It remains to be proved; Estraven and I proved nothing except perhaps a rather subtler point.”

“Love between man and woman is impossible because there must not be sexual intercourse, and friendship between man and woman is impossible because there must be sexual intercourse.”

“Remember, Vampyres are dead. While a female Vampyre can go through the motions of sex, since their flesh retains normal flexibility and warmth, they are unable to truly participate. So having sex with a female Vampyre is a cross between intercourse with an unconscious woman and intercourse with a corpse.”

“Sexual intercourse began in nineteen sixty-three (Which was rather late for me) between the end of the Chatterley ban and the Beatles' first LP.”

“As for sex. Well, of course I could’ve had sex. Guys will have sex with a watermelon if they’re desperate enough. Lots of girls try to prove their love by having sex. It only proves they’re having sex.”

“She was a nice little girl, simple and true, and tremendously frightened of sex. I told her it was beautiful. I wanted to prove this to her. She let me prove it, but I was too impatient and proved nothing.”