and I wouldn't describe it as commonly accepted. It is commonly accepted that diamonds are valuable. It is also provably false (they have no resale value and their price is fixed by a cartel). According to Bob & Tom (which isn't exactly the most reliable source) 66% of people surveyed believe poinsettias are poisonous. While "technically" true it would take so much as to be prohibitive. I'd view the roman empire part like that. The barbarian armies may have had roman training, but so did the romans. I'd say the fall of something as vast and complex as the Roman Empire being blamed on one thing (barbarian influence) is being a little naive... Wouldn't you?