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.
Agreement about the facts and when they change — that is, a consensus about what is in the ledger, and a trust that the ledger is accurate — is one of the fundamental bases of market capitalism.
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The evolution of the ledger
For all its importance, ledger technology has been mostly unchanged … until now.
Ledgers appear at the dawn of written communication. Ledgers and writing developed simultaneously in the Ancient Near East to record production, trade, and debt. Clay tablets baked with cuneiform script detailed units of rations, taxes, workers and so forth. The first international ‘community’ was arranged through a structured network of alliances that functioned a lot like a distributed ledger.
A fragment of a late Babylonian cuneiform ledger, held by the British Museum, 58278
The first major change to ledgers appeared in the fourteenth century with the invention of double entry bookkeeping. By recording both debits and credits, double entry bookkeeping conserved data across multiple (distributed) ledgers, and allowed for the reconciliation of information between ledgers.
The nineteenth century saw the next advance in ledger technology with the rise of large corporate firms and large bureaucracies. These centralised ledgers enabled dramatic increases in organisational size and scope, but relied entirely on trust in the centralised institutions.
In the late twentieth century ledgers moved from analog to digital ledgers. For example, in the 1970s the Australian passport ledger was digitised and centralised. A database allows for more complex distribution, calculation, analysis and tracking. A database is computable and searchable.
But a database still relies on trust; a digitised ledger is only as reliable as the organisation that maintains it (and the individuals they employ). It is this problem that the blockchain solves. The blockchain is a distributed ledgers that does not rely on a trusted central authority to maintain and validate the ledger.
