I am going to consider some common and, for the most part, fairly unreflective reasons for thinking that homosexuality is a bad thing and, therefore, something that should be extirpated, if that is possible, or suppressed, by, most obviously, legal prohibition or, falling short of that, by moral or social pressure. These reasons are five in number: homosexuality is held to be unnatural, abnormal, a perversion, morally wrong or sinful and aesthetically repellent or disgusting. The first three of these unfavourable characterisations of homosexuality apply to it primarily as an orientation, a disposition to engage in homosexual activity, whether the disposition is manifested or not. The other two, the moral and aesthetic ones, so far as most of their proponents are concerned, apply only to homosexuality, as manifested in actual conduct. The desire to sin, after all, is a necessary condition of virtue. There is no merit in not doing things one has no desire to do. Similarly the desire to do something disgusting is hardly, in itself, disgusting.

My subject spreads beyond the general formula of the series: philosophy and psychiatry. But it has a psychiatric component. Up until recent times, at any rate, text-books of psychiatry have classified homosexuality as an abnormality or ‘personality disorder’ and, within that general area, as one of the sexual perversions. This way of classifying homosexuality may be seen as reflecting the more primitive, commonsensical conception of homosexuality as unnatural.