 Sex raises fascinating issues. Rooted in our biology, pervaded by our intentionality, and (normally) directed at other human beings, sexual desire is complex and not confined to specific mating seasons. Its pleasures are powerful and have ruined many lives. Men and women seem to exhibit, desire, and experience sex differently (e.g., men, much more than women, consume pornography, have sex with prostitutes, frequent strip clubs, and have fetishes [Buss 2016, esp. chs. 2 and 3; Laumann et al. 1994, esp. pt. II; Margolis 2004, esp. ch. 1–3; Symons 1979, esp. chs. 1 and 7]). Why this is so, is debatable (Soble 2008: ch. 10; Wertheimer 2003: ch. 3) but these issues make it crucial to understand sexual desire, pleasure, activity, and preferences, and to explore the moral aspects of sex.