Even lesser, more specific initiatives command a reverence out of proportion with actual facts. Look at the early-education program Head Start. Unimpeachable in its goals and seemingly sound in its logic, it’s one of the most celebrated, cherished antipoverty initiatives of the last half-century. Discussion about it has almost always centered on how best to protect or, ideally, expand it, because it so surely accomplishes such great good.

Except maybe it doesn’t. As Joe Klein reported in Time magazine earlier this summer, a comprehensive impact study for the Department of Health and Human Services raised questions about whether Head Start in its current form had all that much lingering benefit to its participants. That the department did so little to acknowledge or publicize these findings suggests the extent to which the program is considered gospel.

In government and so much else there are a multitude of options to weigh, a plenitude of roads to take and a tendency to puff up the one actually taken, because doing so squelches second-guessing and quells doubt.

Image Frank Bruni Credit... Earl Wilson/The New York Times

“The minute you decide to buy the Toyota, your evaluation of it goes up,” said Jon A. Krosnick, a social psychologist at Stanford University who studies attitude formation. “You overly romanticize it.”

The same goes for religious creeds, political theories or, for that matter, management philosophies. Corporate America embraces one eureka approach after another, be it employee ownership or management by objective or the cult of the charismatic C.E.O., and when such movements begin, “They’re considered like the invention of fire,” said Eric Abrahamson, who teaches at Columbia University’s graduate business school. “They do everything, they work everywhere, with great consequences. Just like religions, they give a whole explanation of the world.” That is, until they are swept aside in favor of the next movements, to be clung to as fiercely and blindingly as their predecessors.

Clarity seduces. So does simplicity. We don’t want to hear that different skills produce different results in different contexts, but rather that there are “7 Habits of Highly Effective People,” the number specific, finite. We like to believe that triathlon training will trump genes and keep all major illness and minor sagging at bay, and that the metabolic alchemy of a cabbage-soup diet or a no-carb diet or some other diet will work wonders and obviate humdrum moderation. Magical thinking, all of it.