A few weeks ago, Robin Hanson posed a lunchtime challenge: What is the difference between Left and Right?  The point of the question, of course, is not to explain how every self-styled leftist differs from every self-styled rightist.  The point is to identify unifying themes that generalize broadly across time and space.

There are many prominent candidates, like:

1. Leftists care more about equality, rightists care more about efficiency.
2. Leftists care more about the poor, rightists care more about the rich.
3. Leftists are more secular, rightists are more religious.

To my mind, though, all these theories overintellectualize Left and Right.  Neither ideology is a deduction from first principles.  Not even close.  What binds Leftists with fellow Leftists, Rightists with fellow Rightists, is not logic, but psycho-logic.  Feelings, not theories.

What’s my alternative?  This:

1. Leftists are anti-market.  On an emotional level, they’re critical of market outcomes.  No matter how good market outcomes are, they can’t bear to say, “Markets have done a great job, who could ask for more?” 

2. Rightists are anti-leftist.  On an emotional level, they’re critical of leftists.  No matter how much they agree with leftists on an issue, they can’t bear to say, “The left is totally right, it would be churlish to criticize them.” 

Yes, this story is uncharitable and simplistic.  But clarifying.  Communists and moderate Democrats are vastly different, but they have something in common: Free markets get on their nerves.  Nazis and moderate Republicans are vastly different, but they too have something in common: Leftists get on their nerves.  Within each side, the difference between moderates and extremists is the intensity of their antipathy, not the object of their antipathy.

To see my point, imagine two grand conventions.  The first is for all self-identified Leftists.  The second is for all self-identified Rightists.  Now imagine a grand Compromise Statement able to command the assent of 80% of the attendees.  I say the Left’s Compromise Statement will consist in a bunch of complaints about markets.  And I say the Right’s Compromise Statement will consist in a bunch of complaints about Leftists.

To be clear, my theory of Left and Right is tentative.  If you know of relevant evidence one way or the other, I’m listening.