One type chooses, for non-economic and non-scientific reasons, a political stance and a set of political allies, and twiddles and tunes his or her assumptions until they yield conclusions that fit their stance and please their allies. The other type takes the carcass of history, throws it into the pot, turns up the heat, and boils it down, hoping that the bones will yield lessons and suggest principles to guide our civilization’s voters, bureaucrats, and politicians as they slouch toward utopia.