Officially, a big part of the federal government shut down late last month. In important ways, however, America’s government went AWOL almost two years earlier, when Donald Trump was inaugurated.

After all, politicians supposedly seek office in order to get stuff done — to tackle real problems and implement solutions. But neither Trump, who spends his energy inventing crises at the border, nor the Republicans who controlled Congress for two years have done any of that. Their only major legislative achievement was a tax cut that blew up the deficit without, as far as anyone can tell, doing anything to enhance the economy’s long-run growth prospects.

Meanwhile, there has been no hint of the infrastructure plan Trump promised to deliver. And after many years of denouncing Obamacare and promising to provide a far better replacement, Republicans turned out to have no idea how to do that, and in particular no plan to protect Americans with pre-existing conditions.

Why can’t Republicans govern? It’s not just that their party is committed to an ideology that says that government is always the problem, never the solution. Beyond that, they have systematically deprived themselves of the ability to analyze policies and learn from evidence, because hard thinking might lead someone to question received doctrine.