One may say that anything fashionable is accepted and that anything unfashionable is banned.

But that does not help one to explain to one's self the oddity of some social conventions.
Oddest of all our Roman social conventions is the contrast between the insistence on complete concealment of the human figure everywhere else and the universal acceptance of its display at the Thermae.
At home, if receiving guests, on the streets, at a formal dinner, at Palace levees, at the Circus games or in the Amphitheatre, a man must be wrapped up in his toga.

Any exposure of too much of the left arm, of either ankle, is hooted at as bad form, is decried as indecent.
So of our ladies, on dinner sofas, on their reclining chairs in their reception rooms, in their homes, in their litters abroad, at the Amphitheatre or at the Circus games, from neck to instep they are muffled up.

If one catches a glimpse of a beauty's ankle as she goes up a stair, one is thrilled, one watches eagerly, one cranes to look.
Yet one encounters the same beauty the same afternoon in a corridor of the Baths of Titus, with nothing on but a net over her elaborate coiffure and the bracelet with the key and number of the locker in which the attendant has put away her clothing and valuables and one not only cannot stare at her, one cannot look at her, not even if she accosts one and lingers for a chat.
I have pondered over this, the most singular of our social conventions, and the most mandatory and inescapable; and the more I ponder the more singular it seems.
Yet it is real, it is a fact.

One meets the wives of all one's friends, the wives of all Rome's nobility, naked as they were born; they mingle with the men in the swimming pools, in the ante-rooms, in the rest-rooms, everywhere except in the shower-bath cabinets and the rubbing-down rooms; one swims with them, lounges with them, joins groups of chatting gentlemen and ladies, chats, goes off, and all the while one cannot, one simply cannot stare at a nude woman, any more than any of the women ever stares at any man.
It is a social convention.