If Julius Caesar lived to invade Parthia?

[Frank]

I think the consequences of a third big culture are widely underestimated in such discussions. The roman empire was already splitted in 2 big cultures, the greek and the roman one. With Syria they had a province which was a mix of greek and oriental culture. Later more oriental influence arose with North-Mesopotamia and Palmyra. And we know, what consequences this small oriental part of the empire had on the roman society and politics in the 3rd/4th century.

Now imagine, the romans would really had conquered the economic core of the East: Armenia, Mesopotamia, Media, Susiana, Persis. Thats the minimum you have to control directly (province), in order to be succesful, imho. The consequences of such a powerful 3rd culture in the empire would be unpredictable.

Some historians argue, that this was one of many reasons, why Hadrian, the greek-roman philosopher on the throne, refused to continue Trajans already mostly failed campaign. During the campaign and his time as governor of Syria he was faced with the oriental culture. And for a person like Hadrian, the idea of a 3rd big oriental culture might have been a nightmare.