In 2009 the Nigerian writer Chimamanda Ngozi Adichie gave a fabulous TED talk called “The Danger of a Single Story.” It was about what happens when complex human beings and situations are reduced to a single narrative: when Africans, for example, are treated solely as pitiable poor, starving victims with flies on their faces.

Her point was that each individual life contains a heterogeneous compilation of stories. If you reduce people to one, you’re taking away their humanity.

American politics has always been prone to single storyism — candidates reducing complex issues to simple fables. This year the problem is acute because Donald Trump and Bernie Sanders are the giants of Single Storyism. They reduce pretty much all issues to the same single story: the alien invader story.

Every problem can be solved by finding some corrupt or oppressive group to blame. If America is beset by wage stagnation it’s not because of intricate structural problems. It’s because of the criminal Mexicans sneaking across the border or it’s because of this evil entity called “the banks.”