A key part of the cultural argument is about the change in art over the centuries. Of the sculptor of the Tetrarchs, the author says:
> The artist is not trying to represent the emperors photographically, but rather trying – and succeeding – at representing the ideal emperors, who fully embody the qualities an emperor should.
And:
> Often this transition is, I think, misunderstood by students whose knowledge of artwork essentially ‘skips’ Late Antiquity... and leads some to conclude that the fall of Rome made the artists ‘bad.’ There are two problems: the decline here isn’t in quality and moreover the change didn’t happen with the fall of the Roman Empire but quite a bit earlier.
How do we know that?
One interpretation of the Tetrarchs sculpture vis-a-vis the "verist" sculpture c. 60 BC is that the artist was trying to do something different. Another is that he was just less capable. The earlier artist could capture a realistic portrait of an individual; the later artist couldn't.
How do we know that the first interpretation is the right one?
The author's argument is that the later artist was still really skilful - as he puts it, "look at those folds!" Yeah, sure, he sculpts way better than I could! But that doesn't seem to prove that he is as skilful as the first artist.