But then he gives away the game by pointing to the normative assumptions at the basis of his so-called positive analysis: a high value placed on individual freedom as opposed to human community, a dim view of the democratic political process, a bias in favor of formal mathematical models, and heavy reliance on statistical evidence. Change these assumptions and you get an alternative approach to positive economic analysis that often produces much more interesting insights, and very different policy conclusions.
Glaeser seems to think his assumptions are obviously true, and should be accepted by everyone. In fact, they are the product of a particular worldview that is not universally accepted, nor should it be. I for one believe in the importance of community, democracy, informal or heuristic reasoning, and the validity of all kinds of evidence in social science, including both statistics and historical narrative. And yes, I therefore hold different normative positions from Prof. Glaeser on a lot of issues.