Closely linked to the purpose of sex, especially when considering natural moral law (however don’t forget Aquinas’ argument about the majority). Kant is unlikely to accept. Its hard to know how it could be universalised, though it would be possible. Technically is someone is gay, then any universal maxim would logically only apply to them e.g. “If I am gay it would be right for me to be in a gay relationship.” This can be universalised as it would only apply to gay people, not heterosexual. However as he saw sex as part of a marriage contract, that would rule out homosexuality, unless he attempts to argue that gay marriage is permitted. Utilitarianism uses the principle of utility and its difficult to see, particularly in Act utilitarianism, how it would be against the greatest good. Rule utilitarianism may argue against it but it would have to be justified according to the principle. Virtue ethics would have to consider the virtues and how homosexuality may have an effect on them. If love, compassion, loyalty and honesty are seen as important virtues in a relationship then it is possible that homosexuality is permissible if they are present.