Blockchain is just a database that is 1) public 2) append only If you don't have mining, anyone can append to such blockchain at no cost, so it's defenseless a

Blockchain is just a database that is 1) public 2) append only If you don't have mining, anyone can append to such blockchain at no cost, so it's defenseless against bad actors, so it must have a set of trusted appenders. If you want trustless public database, you must have mining. Mining is costly, so you must have a currency.