What caused the inflation?

Source: EconLog
by Scott Sumner

“Consider the following two claims: 1. Given that NGDP quickly returned to the pre-Covid trend line, the recent bout of high inflation was caused by supply problems. 2. Given the recent supply problems, the recent bout of inflation was caused by the decision to bring NGDP quickly back to the previous trend line. If you see the world the way I do, it’s almost physically painful to read the media as they debate the cause of higher inflation. It makes my hair hurt. What caused the recent bout of inflation? What do you mean by ’cause?'” (111/15/21)