Scientists have started to provide provocative answers by looking at the roots of morality. The influential psychologist Jonathan Haidt has surveyed the world's cultures and suggested that virtually everyone is born with an innate propensity for five broad moral instincts: fairness, not harming others, loyalty to one's group, respecting authority, and purity.
And in psychological experiments, conservatives value all five of the instincts, yet liberals tend to put far more weight on the first two - fairness and not doing harm - while discounting the other three.
It is easy to see how these play out in our political life. For conservatives, loyalty to a group easily translates into a suspicion of outsiders and, therefore, say, a discomfort with immigration. If respecting authority is a central moral value, then burning a flag is deeply offensive. Liberals want to talk about what is fair, and whether anyone is being hurt, while conservatives respond that liberals are missing the point.
There's more, a lot more. In fact, the entire post is well worth clicking over to read.
I've previously posted on the differences between liberals and conservatives, here and here. Now it seems that the discipline of psychology may provide empirical evidence to confirm our gut feelings.