Blockchain

Strip away the slogans and a blockchain is a shared notebook. Many machines keep a copy. They use a rule — work, stake, or something else — to agree which page comes next. Change an old payment and the links that follow no longer match, so honest copies ignore the broken version.

That design has costs: public history, fees when space is scarce, and upgrades that still need people to coordinate. “Code is law” was always a slogan. The ledger is rigid; the community around it is not.