Long before gender theory became a principal target of the right, it existed principally in academic circles. And one of the leading thinkers in the field was the philosopher Judith Butler. In “Gender Trouble” (from 1990) and in other works, Butler popularized ideas about gender as a social construct, a “performance,” a matter of learned behavior. Those ideas proved highly influential for a younger generation, and Butler became the target of traditionalists who abhorred them. A protest at which Butler was burned in effigy, depicted as a witch, inspired their new book, “Who’s Afraid of Gender?” It covers the backlash to trans rights in which conservatives from the Vatican to Vladimir Putin create a “phantasm” of gender as a destructive force. “Obviously, nobody who is thinking about gender . . . is saying you can’t be a mother, that you can’t be a father, or we’re not using those words anymore,” they tell David Remnick. “Or we’re going to take your sex away.” They also discuss Butler’s identification as nonbinary after many years of identifying as a woman. “The young people gave me the ‘they,’ ” as Butler puts it. “At the end of ‘Gender Trouble,’ in 1990, I said, ‘Why do we restrict ourselves to thinking there are only men and women?’ . . . This generation has come along with the idea of being nonbinary. [It] never occurred to me! Then I thought, Of course I am. What else would I be? . . . I just feel gratitude to the younger generation, they gave me something wonderful. That also takes humility of a certain kind.”