Observations About Underlying Assumptions

In my years of arguing with people on the internet, I've noticed that it is extremely difficult to have a reasonable debate with someone who holds different underlying beliefs & assumptions, unless you focus on a narrowly specific topic and stick to it. Otherwise you end up talking past each other. It can happen in person also, but the internet exacerbates the problem since it is easier to hold an unyielding/uncompromising position in this less personal format. This happens all the time in most unstructured debates between theists and atheists. It goes something like this:

Theist: I believe this because god said x

Atheist: I don't believe in god. God didn't say anything because he doesn't exist.

Theist: My scripture teaches us x

Atheist: Your scripture is just a bunch of myths

Theist: These truths are self-evident to human reason

Atheist: No they aren't.  You only believe them because of your religion. Why can't you see reality?

Theist: I see reality just fine. You are deluding yourself in thinking your human understanding is the extent of reality. Why won't you recognize these self-evident truths?

And so forth.

Unfortunately this type of thing occurs with many topics. Often underlying assumptions are so strong that they are accepted as fact. In effect, both sides are arguing based on a different set of facts. This is not conducive to a useful debate. Take the stimulus. Some believe that Keynesian governmental economic intervention, as exemplified by the New Deal, assisted the U.S. in recovering from the Great Depression, whereas others believe that New Deal policies actually prolonged the depression. If two people who hold these polar opposite views of history debate current economic policy, it will go nowhere. Both have views of the current situation that rest on a different set of perceived facts.