Some of my best, most mind-expanding conversations have occurred with good friends who agree with me on almost everything––but not quite everything. Bottom Line: Want to learn and get smarter by talking to people? Seek out those who agree with you on 99.9% of things, and then push, push, push at the niche-y, hyper-specific areas of disagreement. It’s not about groupthink; it’s not about confirmation bias. It’s about learning on the margin.
Cf. William Deresiewicz.
Introspection means talking to yourself, and one of the best ways of talking to yourself is by talking to another person.