levay discusses "brain mechanisms that are responsible for sexual behavior and feelings"; topics considered include sexual orientation, the evolutionary basis of sex, sexual development, the organization and development of the brain, the neural mechanisms associated with sexual intercourse, gender differences, and gender identity. levay expresses skepticism about the work of sigmund freud, the founder of psychoanalysis, writing that while he once accepted the freudian view that "a young child's relations with his or her parents play a decisive role" in the development of sexual orientation, he rejected it after he came to know large numbers of gay men and lesbian women. levay writes that he doubts that there is anything scientific about freud's ideas.