The latest Fortune features senior editor at large Geoff Colvin‘s analysis of the impact of uncertainty on our sluggish economy.

Economic uncertainty, especially policy uncertainty, is greater than it has been in many years. And if you’re wondering why the U.S. economy is barely moving or why millions of workers can’t find jobs, extraordinary uncertainty is a major part — maybe the largest part — of the answer.

High uncertainty creates a loop of paralysis, and that’s what we’re in right now. Policymakers have no idea what’s going to happen, so they sit on their hands, as the Federal Reserve did recently. …

… The business leaders were most uncertain about tax and regulatory issues. Those things are always changeable, but the potential swings could make you dizzy. After the Supreme Court upheld Obamacare in June, Mitt Romney and Republican congressional leaders promised to repeal it if they win the elections in November. So the biggest-ever regulation of the largest sector of the world’s largest economy, affecting every employer and individual in the country, either will continue as the law of the land or will disappear. Who can even think about planning in those circumstances?