On July 20, Vitalik Buterin responded to a question on social media about "what is a universal blockchain" and said that blockchain is a 'truth machine'. In a specific sense, it provides a consensus approximate truth about when a message was sent, but it will not tell you whether the moon landing was true. This greatly reduces the attack surface of the blockchain, but it does mean that we need other tools to actually perform (or assist) the latter truth discovery.