I am a persistent devil's advocate.
For better or worse, I stick to the guns currently at my hip and will argue semantics until we all agree. And I rarely agree to disagree. In my view, there is no right or wrong, logic rules all.
I believe that all views come from a logical process, even the craziest ones. But somewhere along the way a false assumption is made. This is almost a corollary of the principle of explosion (the idea that from a contradiction any statement can be "proven" true).
I have also noticed that my opinions on the world change much quicker than I generally think they do. Small changes, of course, but numerous and subtle changes that seem innocuous at the time. So when I am presented with a question like "How do you feel the rich being taxed more?", sure I have my pre-packaged answer (Yes, please). But that is an answer based on an earlier set of assumptions; a previous version of my knowledge base. Why I should I provide the instinctual response when this is a perfect opportunity to re-evaluate my position? So I say "I don't know, a single percentage across the board seems the most fair," and the conversation escalates.
Because of this urge for impromptu reevaluation (and my view that all ideas have a logic to them), there are very few positions that I will not assume, if only temporarily, until I see that it does not agree with my own current assumptions and knowledge about the world. And by committing myself to one side of an argument I am forced to fight for its logic and determine its assumptions (and their validity).
But this is where I often lose people. From proposals to "agree to disagree" to accusations of a moving target, people often express frustration at my methods of argumentation. For example, as the conversation evolves I may agree with the point that the burden that a given percentage places on lower-income individuals is much greater than that incurred by a wealthier person. So I parry, and adjust.
Regardless, whether we delve into the rather interesting discussions of how monetary impact is felt, what puts someone in a given socio-economic status, the semantics of the word "burden" and how that applies to a societal contract, or any of the other myriad aspects to this issue, the argument continues and expands.
Eventually, if the person is patient, we may eventually get back to the primary issue and we may either agree or disagree. But things get funny at this point. People actually dislike it more when I agree with them! I assume that, because people seem to dislike arguing, their shock at my initial response (and many of the points that I make along the way) is what keeps them invested in the discussion. Finding out we are in agreement confuses and frustrates them because they have invested this time and energy on what they now see as a lost cause.
But they miss the point.
I generally don't really care whether we agree or disagree. Neither of us are likely to decide whether or not we tax the wealthy at 50%, so it doesn't really matter what we think. Even if we eventually have a chance to vote on the issue, it is rarely so cut-and-dry—we vote on bills, not concepts. What I care about is the path to the viewpoint. After the conversation I understand why they have their opinion. I have a greater understanding of where they're coming from, of how they may feel about other issues, and maybe even of the issue itself. And I think we're both better for having had the conversation.
So, in my eyes, playing devil's advocate is much more than just proposing an alternative viewpoint. I force it until it breaks, until I find what stays whole. Until I find out a little bit more about the idea, the other person, or even myself. I dedicate myself to the proposition, not its truth.
Not entirely relevant, but important to keep in mind: "Believe nothing, no matter where you read it or who has said it, not even if I have said it, unless it agrees with your own reason and your own common sense." –Buddha