Freud’s argument is rather clever: morality rests on notions of disgust, cultivated in the individual by the wider culture, in order to provoke revulsion at certain behaviors. But the basis for that revulsion is not rational. It is merely that of a social convention. A man might object to using his girlfriend’s toothbrush ostensibly on grounds of hygiene; but he will rather enjoy giving her a passionate kiss that involves the same compromise of his personal cleanliness. And so, Freud argues, morality is really a matter of cultural tastes.
