01/21/2011 06:12 pm ET Updated May 25, 2011

Conservatives' Faith-Based Reality Is Dangerous

American conservatives like to demonize the "mainstream media" as a creature of the left, at odds with morality itself. But conservatives' real problem is with reality. Facts, in their view, should either serve their ideological purpose or go away. Reporting facts that do not fit the conservative creed must be part of a liberal plot.

My new book, The Price of Everything, has just been subjected to the right's peculiar acid test. The book draws on research by economists, biologists and psychologists to propose that people -- and societies -- are hard-nosed about their decisions: we evaluate the costs and benefits of the options we face even in the most personal domains of life, to decide whether to get married, speed on the highway, or even join a religion.

The proposition has distressed Jonathan Last of the Weekly Standard. Writing in the Wall Street Journal, he argued that The Price of Everything is a collection of "liberal pieties dressed up as logic." In Mr. Last's view, the evolution of societies is a matter of good ideas (those espoused by conservatives, of course) emerging from out of... somewhere to push bad ideas aside. My argument that environmental pressures and material incentives sway humanity's choices injures his faith in a world shaped by personal responsibility, molded by "beliefs, doctrines and worldviews."

My book can survive Mr. Last's discomfort. What is concerning about his diatribe is the window it offers into a conservative mindset impervious to fact. In the worldview of the ideologue improvement arrives by the hand of good conservative intentions, evidence to the contrary be damned. His faith-based approach to reality would be entertaining. But the war in Iraq, championed by neocons who wrote the script to a just and rapid victory on the basis of their beliefs alone, underscores just how dangerous this right-wing idealism is.

About The Price of Everything Mr. Last is also wrong. His assault upon my supposed "liberal pieties" is ultimately undone by his inability to make his arguments fit social, economic or historical fact.

He believes that a proper family must be heterosexual and monogamous. Societies in which other forms of mating prevailed had to be deviant and corrupt. He thus takes offense at my proposition that polygamy -- a once common institution -- declined around the world because of economic incentives: it undermined social cohesion because it allowed rich men to hoard women and condemned poor men to never find a mate. This put polygamous groups at a disadvantage compared to monogamous societies -- making them more prone to civil strife.

Mr. Last would have us believe instead that polygamy declined because the right belief set -- "Judeo-Christianity" -- emerged to do away with the barbarous practice, presumably convincing people that it was immoral for one man to mate with more than one woman. "Ideas matter," he says.

History matters too. The fact is that "Judeo-Christianity" did not bring about the decline of polygamy. Saint Augustine called monogamy a "Roman custom." And polygamy remained a common institution well into "Judeo-Christian" times. Among Jews, the practice was only prohibited among the Ashkenazi in the 11th Century of the Christian era. Polygamy also popped up across Christendom -- including among the Mormons in the United States 150 years ago. It was an entrenched institution among the European nobility throughout the Middle Ages, when Kings and sundry royals kept stables of concubines and servants to mate with.

Mr. Last's doctrinal approach to social change also rejects the idea that the family changed because women entered the work force -- increasing their value at home and in society beyond being wombs and homemakers. This contributed to a decline in birth rates across the industrial world. Mr. Last goes to battle against the proposition by arguing that birth rates started declining before women went to work and have declined in countries in which women work little. But he has a muddled grasp of his facts. He points out that fertility has declined sharply in Iran and Mexico. True. But he somehow overlooks that the labor supply of Mexican and Iranian women grew by more than ten percentage points in the last 30 years.

Mr. Last seems especially upset about the proposition that Americans remain deeply religious due to the depth of poverty in the United States -- which increases demand for religion as an insurance policy -- or salve -- against economic insecurity. Apparently he believes that socioeconomic circumstance has no bearing on people's faith. Belief springs fully formed from... somewhere.

It must be difficult to go about life believing that all good comes through the agency of one's own ideas. The belief may help rally the faithful. But it is a fragile, brittle world-view, prone to be brought down by even the slightest shade of doubt or contact with the real world. The Price of Everything, which proposes that ideas emerge from economic considerations, is an unwelcome shake to this shaky edifice.

That is, however, what honest inquiry is meant to do.