- What does it mean when we say that in blockchain, consensus determines the truth?
In a blockchain (decentralized network or database), a consensus mechanism is used to make sure that all information that goes into the ledger is valid and that all nodes agree on that. The consensus is reached when different nodes compare their own copy of the ledger with the other nodes in order to make sure that they all match and, this way, reaching an agreement (truth) that the transaction is a valid one or not. By doing this, the network can verify all the transactions and guarantee its users the integrity of the information existing in the blockchain, removing the need for trust and replacing trust for auditing and verification.
- How is this different from how truth is determined in a central database?
In a central database, there is no consensus mechanism and the truth is determined by the rules established by a central authority. This central authority (single party) decides which information can go into the blockchain or not, forcing the users to trust (blindly) in this single entity for validating the transactions and maintain the integrity of the information existing on the database.