The ethical importance of dialogue can hardly be overstated. The key to ethical dialogue is mutual acceptance of sincere questioning about reasons. To ask a question is not to make a counter-assertion, and no one should ever take offense at a sincere question.
To qualify as based on good judgment or sound reasoning, a commitment or one’s reasons for holding it must be explainable in a shareable way. Sharing of the kind of meaning-based material inference used in everyday reasoning and judgment (as well as most philosophy) is a social process of open-ended dialogue.
The world’s oldest preserved examples of such rational dialogue (or any kind of rational development) are contained in the works of Plato. Earlier figures just wrote down what they saw as the truth. Plato provided many examples of a method of free inquiry. (Aristotle says the atomist Democritus was another initiator of rational inquiry, but the works of Democritus do not survive.) This is yet another reason why Hegel called Plato and Aristotle the greatest teachers of the human race.
Plato bequeathed to us many idealized examples of reasoning by dialogue. He raised them into an art form, creating a new literary genre in the process. His dialogues vary in the degree to which they approximate free open-ended discussion; most often, one character leads the discussion through question and answer, and sometimes even the question and answer is limited. However, since Plato’s dialogues are like plays portraying self-contained conversations, they are very accessible.
The style of question and answer often practiced by Platonic characters like Socrates — commonly known as Socratic method — provides a model for how anyone can contribute to such a development. The questioner tries to reason only from things to which the answerer agrees, but often has to keep questioning to draw out the needed background.
In a fully free and open dialogue characterized by mutual recognition, any party may make contributions of this sort. As Sellars and Brandom would remind us, to assert anything at all is implicitly to take responsibility for that assertion, which is to invite questioning about our reasons.