[N]o conduct otherwise immoral should be excused because it is sexual conduct, and nothing in sex is immoral unless condemned by rules which apply elsewhere as well. (Goldman 1977: 280)
This is true at a general level because the same general moral features (e.g., harm) affect sexual acts. But it might be false at more specific levels: sexual violation of the body by a penis or an object makes the violation distinct. This has to do with how one experiences sexual bodily violations, thereby making sexual consent a crucial moral aspect of sexual relations (Wertheimer 2003: 107–112). If virtue ethicists are right, actions can be right and wrong because they are sexually temperate and intemperate: seducing the ex-boss’s husband is vengeful or intemperate, depending on the motive (Carr 2007; Halwani 2018a, 2018b; Piers 1999). The specialness of sex might be explained by sexual desire’s rootedness in biology and its being directed at the bodies of other human beings (Dent 1984: ch. 2 and passim).
Consent is crucial because (a) it transforms an otherwise wrong act into a permissible one (though not necessarily to a good act); (b) in heterosexual sex, men and women might importantly differ when it comes to sex; and (c) sexual violation is typically experienced as very harmful (Wertheimer 2003: 119–121).
On such views, consensual casual sex between two strangers is impermissible
There is general consensus among philosophers that valid or genuine consent (henceforth “consent”) by all the parties to a sex act is necessary and sufficient for the moral permissibility of the sex act (Archard 1998; Mappes 1987; Miller & Wertheimer 2010; Primoratz 2001; Wertheimer 2003; but see Pateman 1988), though what valid consent consists of is an intricate issue (to which Wertheimer 2003 is dedicated). Yet the sufficiency of consent can be questioned. If, for example, sexual desire by nature objectifies, as the Kantian view has it, then the consent of the parties is insufficient-they consent to a wrong action (see below).
Another reason to reject consent’s sufficiency stems from some conceptions of what marital sex is. The theory of New Natural Law considers only marital sex-which it understands as referring to sex acts between married partners who do it from the specific motive of the good of marriage (what this means, though, is unclear)-is morally permissible (even good). The main reasons are the theory’s view of marriage, which, following Thomas Aquinas, is understood as a basic good, and the view of marital sexual acts as reproductive and unitive, as two-in-one flesh communions. Thus, although consent to the sexual act is necessary, it is not sufficient: the sex has to be done from the motive of the good of ; George & Bradley 1995; Lee & George 1997).
Two prominent objections to the New Natural Law view are (1) that the view of marriage is both undefended and implausible: the connection between reproduction or biological two-in-one union and the morality of sex is unclear, and (2) that it is unclear why other goods (sexual pleasure) are ruled out as basic (Koppelman 2008; see also Biggar & Black 2000).
New Natural Law is a version of any type of view that limits the morality of sexual acts to specific domains. In addition to marriage, love is another such domain. A view confining sex to love need not insist also on marriage, on only two love partners, or that they be of different sex/gender. It requires only the presence flirt of love. Other versions require only affection or a mutually respectful relationship (Hampton 1999; Nussbaum 1995).