Let’s start with a simple database on your PC - only you can edit it. You want everyone to participate it instead, so you make it peer-to-peer. Of course, it ends up as a total mess, with people deleting what others have written. So, you make it append-only, so you cannot edit what has been before. But it’s still a complete mess. Now, you restrict who can append to it, and their additions need to be verified by everyone else, and now it finally makes some sense. This is consensus, but local consensus. The next question then becomes, how can you retain this pattern, but start making it more accessible once again, like it was before?