Camels and Ideas

So, in the prompt Mr. Chaput asked, "How do they move goods and ideas?", and because we just read about trade and camel saddles, I am going to assume that goods and ideas travel by trade and camel saddles. I do not believe that any society actively shares their ideas(unless they send missionaries). I can't imagine a king sending out a subject to go from town to town sharing new ideas. I believe ideas are exchanged passively along with goods. When a trader arrives in a new town he might sit down at a bar and talk about his customs to his fellow men. I can easily picture a ancient greek merchant enter a Roman restaurant and ask for a menu and when they told him that they don't have menus because they don't have written language, he would get irritated and tell them that back in his country they have this awesome thing called the alphabet. Goods and travel by the Indian Ocean and camels. I assume that when nations fall, people seek out guidance and are more open to new ideas.