Weak Subjectivity

So, we may define objectivity as the ability for a new node to join the network and quickly “learn” which is the active chain (also referred to as the longest chain). Put in another way, objectivity means that new nodes can easily synchronize to the valid state of the system because there is only one path that can be considered the longest.

In this case, the nodes need to help each other when reaching consensus instead of following a deterministic rule, such as the “longest chain rule.” And that’s what gives a certain degree of subjectivity to some blockchain networks.

So we may say that subjectivity is related to the idea that certain nodes need to receive information from other nodes when trying to determine the current state of the ledger. Note that this is not related to consensus achievement but rather to determining which chain is the active one.

So, if a node remains online continuously, there won’t be a subjectivity problem because they will be able to quickly determine which ledger is the “valid” one. But if the node goes offline for a long period of time, they will need to rely on other nodes, and that is where subjectivity happens. Still, the subjectivity is considered weak because it only occurs in two situations: when new nodes join the network, or when nodes go offline for long periods.