We liberals like to flatter ourselves by proclaiming our allegiance to fact. In the immortal words of Stephen Colbert, for us, mere "truthiness" will not suffice. We demand evidence, research, science -- Truth itself. But on so many of the social issues liberals care about, concrete fact is a rare commodity. Take education policy, a beat I've been covering for over two years. We know our schools aren't good enough: There is a dropout crisis among blacks and Latinos, colleges are forced to reteach algebra and basic essay writing, and classrooms are becoming more racially and socioecomically segregated. But beyond these observable trends, we can't agree on much. Liberals are in complete disagreement about how to fix American education, whether the topic is a national curriculum, standardized testing, or how to pay teachers. That's what has made this topic so maddening -- and fascinating -- to cover. Consider charter schools, for example. The White House and Education Secretary Arne...