Consensus refers to a state of agreement amongst the actors. Over the long-term human societies have been reasonably effective at achieving and maintaining consensus. However, achieving consensus in decentralized networks where actors cannot be trusted is challenging. In such cases most approaches to consensus have involved some degree of majority voting where the majority is typically defined in terms of a % of hashing power or token holdings.
A drawback in all such democratic governance models is that the consensus view is not necessarily the best for the long term development of the network. Ideally, we would strive to create consensus mechanisms that identify, promote and implement the best ideas.
Blockchain uses a form of consensus mechanism called Nakamoto Consensus.