The economic approach embraced by the most prominent liberals over the past few years is mostly mechanical. The economy is treated like a big machine; the people in it like rational, utility maximizing cogs...David Brooks doesn't, clearly, understand rationality. If $1 borrowed and spent by the government produces $1.50 in the economy, the government should borrow infinitely! This "regularity" is not reproduced in any rational-optimization model of which this economist is aware.
These models can be used to make highly specific projections. If the government borrows $1 and then spends it, it will produce $1.50 worth of economic activity. If the government spends $800 billion on a stimulus package, that will produce 3.5 million in new jobs. Everything is rigorous. Everything is science.
Moreover, within the discipline, those who believe in optimizing agents, intertemporal tradeoffs, and rationality typically are anti-stimulus. Those who are in favor of the stimulus and who have the ear of the Obama administration - Krugman, Stiglitz, Hall, etc - are typically more solicitous of 'heterodox' behavioral approaches. The Keynesian approach of the Obama administration is predicated on the famous concept of "Animal Spirits".
Brooks has it completely backwards: the administration and its 'technocrats' have relied on empirical regularities which lack theoretical underpinnings. What we need is exactly what November voters demanded: a return to rigor and reasonable intertemporal tradeoffs.