The blockchain is a digital, decentralised, distributed ledger.
Most explanations for the importance of the blockchain start with Bitcoin and the history of money. But money is just the first use case of the blockchain. And it is unlikely to be the most important.
It might seem strange that a ledger — a dull and practical document associated mainly with accounting — would be described as a revolutionary technology. But the blockchain matters because ledgers matter.
Ledgers all the way down
Ledgers are everywhere. Ledgers do more than just record accounting transactions. A ledger consists simply of data structured by rules. Any time we need a consensus about facts, we use a ledger. Ledgers record the facts underpinning the modern economy.
Ledgers confirm ownership. Property title registers map who owns what and whether their land is subject to any caveats or encumbrances. Hernando de Soto has documented how the poor suffer when they own property that has not been confirmed in a ledger. The firm is a ledger, as a network of ownership, employment and production relationships with a single purpose. A club is a ledger, structuring who benefits and who does not.
Ledgers confirm identity. Businesses have identities recorded on government ledgers to track their existence and their status under tax law. The register of Births Deaths and Marriages records the existence of individuals at key moments, and uses that information to confirm identities when those individuals are interacting with the world.
Ledgers confirm status. Citizenship is a ledger, recording who has the rights and is subject to obligations due to national membership. The electoral roll is a ledger, allowing (and, in Australia, obliging) those who are on that roll a vote. Employment is a ledger, giving those employed a contractual claim on payment in return for work.
Ledgers confirm authority. Ledgers identify who can validly sit in parliament, who can access what bank account, who can work with children, who can enter restricted areas.
At their most fundamental level, ledgers map economic and social relationships.