When I was young and naïve, I believed that important people took positions based on careful consideration of the options. Now I know better. Much of what Serious People believe rests on prejudices, not analysis. And these prejudices are subject to fads and fashions.

Which brings me to the subject of today’s column. For the last few months, I and others have watched, with amazement and horror, the emergence of a consensus in policy circles in favor of immediate fiscal austerity. That is, somehow it has become conventional wisdom that now is the time to slash spending, despite the fact that the world’s major economies remain deeply depressed.

This conventional wisdom isn’t based on either evidence or careful analysis. Instead, it rests on what we might charitably call sheer speculation, and less charitably call figments of the policy elite’s imagination  specifically, on belief in what I’ve come to think of as the invisible bond vigilante and the confidence fairy.

Bond vigilantes are investors who pull the plug on governments they perceive as unable or unwilling to pay their debts. Now there’s no question that countries can suffer crises of confidence (see Greece, debt of). But what the advocates of austerity claim is that (a) the bond vigilantes are about to attack America, and (b) spending anything more on stimulus will set them off.