Why so many people believe conspiracy theories

William of Occam would have hated conspiracy theories. A 14th-century philosopher and Franciscan friar, William is celebrated for developing the “law of parsimony,” better known today as “Occam’s razor.” According to the razor principle, the simplest explanation for an event is almost always the best; shave away any extraneous assumptions, and what you’ve got left is usually the truth.

That’s not exactly the way conspiracy theorists think. Either Barack Obama was actually born in Hawaii, or an international plot unfolded over multiple decades to conceal his Kenyan birthplace and install him in the presidency. Either vaccines are safe and effective, or every major hospital and health organization in the world is covering up the fact that they actually cause autism. Never mind the razor — conspiracy theories are nothing but extraneous assumptions.

The question is, Why do so many people believe in them? Why do even the most preposterous theories — the Nazis survived but they fled to the moon; the world is secretly being run by a reptilian elite — have fiercely loyal adherents? There are nearly as many explanations for conspiracy theories as there are theories themselves, but some patterns do appear again and again.

The most common theories are the ones that follow the eddies of politics. As a broad rule, a party or group that’s out of power will be more inclined to believe in conspiracies than a group that’s in power.

“Conspiracy theories are for losers,” says Joseph Uscinski, associate professor of political science at the University of Miami and co-author of the 2014 book American Conspiracy Theories. Uscinski stresses that he uses the term literally, not pejoratively. “People who have lost an election, money or influence look for something to explain that loss.”

So consistent and predictable is this phenomenon that in the U.S. at least, leading conspiracy theories flip almost the moment the presidency does. When Bill Clinton was President, the principle conspiracy tales involved stories of Clintonian cocaine dealing in Arkansas and the alleged murder of Presidential friend and confidante Vince Foster. Once George W. Bush took over, so too did new conspiracy fables, this time involving Vice President Dick Cheney, Halliburton energy and the Blackwater protection company masterminding the Iraq war in order to seize the nation’s oil.

Read more at TIME.