# Consensus Mechanisms

Blockchains (Ethereum included) are ultimately about coming to consensus about the current state of some system (usually a financial system, but not always). It's therefore necessary to understand some of the more fundamental theory behind the protocols that allow computers on a network to come to decisions -- consensus mechanisms. If you truly wish to understand why Ethereum is being built in the way it's being built, becoming familiar with traditional consensus mechanism theory is a requirement. This is particularly true in the context of Ethereum's Proof of Stake consensus protocol which returns to more traditional ideas in the field of consensus mechanisms.

People have been working on consensus mechanisms for decades and there's a mountain of literature about the subject. We've tried to distill this literature into the most important pieces. In this chapter we talk about the key concepts and findings in consensus mechanism research. By the end of this chapter, you should have a solid understanding of what a consensus mechanism attempts to do and the limitations that designers of such mechanisms face.