I've been thinking about what divides the Republican and Democratic parties and here's basically my take on it.
The general goal of the Republican party is to enact a set of laws which codify their party's shared values. They want a flat tax because they think it is fair or just. They want to end welfare because it allows people who don't work to benefit from the labor of those who do. They want to make gay marriage illegal because they think it's wrong for people with the same combination of sex chromosomes to sex each other. By contrast, it seems that the Democratic party generally attempts to enact legislation in order to achieve explicit goals, such as reducing the negative effects of poverty, providing people with healthcare, &c.
This naturally throws up an obstacle to useful political discourse. Republicans tend to look bad when asked what their programs will do because they didn't come to their policy ideas based on studies, but rather came to the studies based on their policy ideas (informed by evaluations of those policies with respect to the moral code they want to enact). Democrats look bad when asked to justify the moral legitimacy of their policies because, well, they were too busy thinking about what they wanted to do.
I think that both parties are being stupid. In order to have a meaningful discussion you need shared assumptions. In this case we need to have candid political discussions about what our shared values are, and the nature of our disagreements. Some values might be hard and non-negotiable. Differences in the abortion debate spring to mind. Others might be more flexible. Many people are willing to budge on completely equal treatment in order to get more equal results, even if they value both kinds of equality. Many are willing to sacrifice some freedoms for increased security.
Issues controlled by hard values need to be decided by the voters and when it comes down to it that means that the most important thing is to recognize the value judgment, describe it accurately, and have both sides of the issue make their arguments to the people. It might even be most appropriate for such issues to be decided by referendum. For just about everything else, we should be agreeing on goals for the nation (informed by our values) and then asking experts for the most effective means towards achieving those goals. We should then recognize what values might be impacted by the most effective means and weigh those values explicitly against the values we were pursuing when considering the end goal of the law. But the most important thing to remember in those sorts of debates is that the process started with agreement that the end goal of the law was worth pursuing. If one particular method looks to infringe too deeply on some values, other methods need to be considered.
I'd like to mention that this is basically a rehashing of my constitutional anarchy ideas within the context of our current political situation. I'd love to add a clause to the constitution that requires a nationwide referendum on any law codifying a value.