When two people disagree about a proposition even though they've thought about it alot, the disagreement is often hard to resolve. There's a gulf of data, concepts, intuitions, experiences, inferences . Some of this gulf has to be resolved by the two people individually trying to collate and present their own positions more clearly and legibly, so that they can build up concepts and propositions in whoever is receiving the model. Also, most new understanding comes from people working on their own or with others who are already synced up——for the most part they already agree on what and how to investigate, they have shared context of past experience and data, they agree on background assumptions, they have a shared language, they trust each other. But still, a lot of value comes from debate. The debaters are forced to make their evidence and logic legible. Ideas are tested against other ideas from another at least somewhat coherent perspective. Analogies and disanalogies are dr...