the great divide in our politics isn’t really about pragmatic issues, about which policies work best; it’s about differences in those very moral imaginations Mr. Obama urges us to expand, about divergent beliefs over what constitutes justice. ... When people talk about partisan differences, they often seem to be implying that these differences are petty, matters that could be resolved with a bit of good will. But what we’re talking about here is a fundamental disagreement about the proper role of government.