Socratic dialogue, where everyone is intent on building up a shared truth. Socrates talks about these two different ways of engaging in dialogue in Plato's works.
Ironically, Plato's Socrates rarely ever actually arrives at what he considers truth, most dialogues just end at an impasse. This is arguably why they're still so readable. They're more about teaching you how to think and question what you know than proselytizing some particular doctrine.