...the purpose of our genitals is to procreate: Sex is for making babies. It may be argued, then, that gay sex is unnatural because it is sexual activity that is divorced from its natural purpose.
This seems to express what many people have in mind when they say that homosexuality is unnatural. However, if gay sex were condemned for this reason, then a number of other, widely accepted practices would also have to be condemned: masturbation, oral sex, sex using condoms, and even sex by women during pregnancy or after menopause. These practices would be just as “unnatural” (and, presumably, just as bad) as gay sex. But there is no reason to accept any of these conclusions, because this whole way of reasoning is faulty. It rests on the assumption that it is wrong to use parts of one’s body for anything other than their natural purposes. Why should we accept that assumption? The “purpose” of the eyes is to see; is it therefore wrong to use one’s eyes to flirt or to give a signal?