There are two broad ethical approaches to sexual matters. The first and older one, long associated with but not exclusive to ‘natural law’ traditions, argues that the very nature of sexual activity makes it highly morally significant. It is the means by which human life is reproduced, involving the most intimate interaction between male and female of the species. This view links reproduction, emotional and physical intimacy, and sexual complementarity, and argues that sex should be placed within these boundaries, thereby rejecting casual, promiscuous, resolutely non-reproductive activity. The second approach rejects the idea that there is anything about sex as such that implies a special morality governing it. The only values are ones relevant to human interactions more generally: they should be consensual, non-abusive, and non-exploitative, but this is compatible with non-heterosexual, multi-partner and causal encounters. At the core of these differences are understandings about human nature including the meaning of sexual identity.