 It is difficult to define “sexual act” or “sexual activity.” Various proposed criteria face difficulties (Soble 2006a). This is especially so when closely related concepts (e.g., “having sex”) do not have the same extension. In ordinary language use, and according to some studies, people distinguish between having sex and sexual activity; they count many activities as sexual but not as having sex, such as solo masturbation, cyber-sex, and even oral sex (Soble 2006a: 15–16). Solo masturbation counts as sexual activity and as a sexual act, but not as having sex. There are a few criteria to define “sexual activity” (Soble 2006a). One criterion is reproduction: for an activity to be sexual it has to be or aim at being reproductive. This faces obvious counter-examples, such as same-sex sexual activities and heterosexual oral and anal sex (Soble 2006a: 18–19). Another criterion is bodily contact: sexual activities are those that involve contact with sexual body parts (though we need to figure out what these are). This fails as a sufficient condition (doctors sometimes have to touch patients’ genitals) and as a necessary one (achieving orgasm during a phone-sex chat) (Soble 2006a: 19–20). 