Kate Millett, whose 1970 book, “Sexual Politics,” made her, as one writer put it, “the principal theoretician of the women’s liberation movement,” and who went on to be a leading voice on human rights, mental health issues and more, died on Wednesday in Paris. She was 82. Her spouse, Sophie Keir, said the cause was cardiac arrest. Living in New York City, they had been going to Paris every year to celebrate their birthdays, she said. Ms. Millett was in her mid-30s and a generally unknown sculptor when her doctoral dissertation at Columbia University, “Sexual Politics,” was published by Doubleday...