Summarizing the Third Century Crisis

[SigniferOne]

Nevertheless, the cultural decline was present since the 250s if not earlier, so long before Aurelian.

Contemporaries certainly thought it had started with the death of Marcus Aurelius and had simply got worse

Cassius Dio and Herodian express the same sentiment - everything was better when Marcus was still emperor. The problem is that I find it hard to believe that the fall of Rome started as early as 180, before the Empire reached its greatest extent (apart from those few months when Trajan believed he was master of Iraq) and before the people reached their greatest wealth (to judge from the number of inscriptions, the Severan age was Empire's golden age).

I don't think that the empire started crumbling as early as 180. That sort of belief stems from Romantics. I've read some histories which state that Rome started falling after Hadrian. Some people say that it was Trajan. Then again others believe Augustus was "the last straw"; in short there's no shortage of ridiculous opinions. Herodian and Dio believe that the world was better under Marcus, which is probably true, but there wasn't a collapse on the scale of the whole civilization falling over, until the reign of Severus Severus. I once read a very pertinent and astute judgment that Severus functionally began the fall of the entire civilization by the fact that he was the first autocratic emperor. The ultimate collapse of the whole civilization is traceable to the utter social breakdown of the 3rd century, isn't it? And who else but Severus is the most proximate cause of that by himself being a model for all the rest to follow. He was a Marius-like brutish soldier, with some pretense to liberal education but more so in contempt to it, attempting a 'reform' with his limited abilities and ruining what was left standing. Once he dismissed the Senate with sheer contempt and changed the Roman constitution towards absolute monarchy, a Diocletian was right around the corner to make that promise completed. And Romans really did not do well with absolute monarchs, so once we see absolutist emperors the entire fabric of the society, its idealistic art and literature, almost immediately collapses, and by the time of Diocletian you get just scraps of what Roman art and literature used to be.