 More recent natural law theorists, however, have presented a couple of different lines of defense for Aquinas’ ‘generative type’ requirement. The first is that sex acts that involve either homosexuality, heterosexual sodomy, or which use contraception, frustrate the purpose of the sex organs, which is reproductive. This argument, often called the ‘perverted faculty argument’, is perhaps implicit in Aquinas. It has, however, come in for sharp attack (see Weitham, 1997), and the best recent defenders of a Thomistic natural law approach are attempting to move beyond it (e.g., George, 1999a, dismisses the argument). If their arguments fail, of course, they must allow that some homosexual sex acts are morally permissible (even positively good), although they would still have resources with which to argue against casual gay (and straight) sex.