Hello. I'm not sure if this is the right place to ask this, but I have a question about informal reasoning, and I was hoping philosophers could assist. Is it fair to say that, if you have a disagreement with someone of a very different viewpoint, you need to appeal to principles they already believe in, and which you also believe, in order to have a meaningful discussion? For instance, if I believe in non-classical logic, and I am trying to persuade a classical logician, I will need to appeal to classical logical principles? Or if I'm a Democrat trying to persuade a Republican? Or a Freudian talking to a Jungian? Or an atheist talking to a rabbi? Or is it possible to have a meaningful discussion without finding any common ground?

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