Just a quick one from a conversation I had today. When we're talking about persuasion, we're really talking about two very different tasks.
Sometimes we argue about how to do things, and normally in that discussion the relevant information is about the world and how it works. The way we convince people in that context is by showing them evidence about the way the world works--facts, studies, that sort of thing.
The other thing we argue about is what we should care about. These sorts of arguments about first order beliefs--which we just take as given in the former class of argument--aren't at all amenable to facts, studies, and figures. Persuasion on these points is essentially an act of conversion and is effected mostly through personal relationships if at all.
Now, first order beliefs are held with varying strengths, and sometimes things that should be higher order beliefs--empirically testable ideas about how the world works--are treated as first order. But, I'd say that's more or less the structure of things.