Good music is a combination of novelty and familiarity, and the same is true for any good art...And conversation is an art form. You need people who are like you so that you can feel comfortable, but who are different enough from you to give you new things to think about.

Precisely. Documents like 'The United States Constitution' exist as a result of the 'intersection of ideas.' Which implies a difference of ideas; coupled with the fact that in that time, an education and quality books were largely something enjoyed by the wealthier classes and included world travel, with 'teachers and institutions' from different parts of the world. So, a wealthy son of a landowning family in France in 1688, might have very different ideas and opinions of how best to govern and inspire economic activity and martial forces and exercise diplomacy than another individual in similar circumstances monetarily, albeit born in Germany, or Sweden, or Japan, etc. -- Differences in ideas and perspectives and approaches coupled with free exchange tend to refine each other.

That's true, but the conversation is completely non productive if you don't share any common premises with the people you are talking to.