Vitalik Buterin coined the term “weak subjectivity” to describe a requirement present on Proof of Stake (PoS) blockchains, where nodes must rely on other nodes to ascertain the system’s current state.
The ability of a new node to join the network and quickly “learn” which chain is active is known as objectivity (also referred to as the longest chain). Alternatively, objectivity means that there is just one path that may be regarded as the longest, which makes it simple for new nodes to synchronize to the system’s current valid state.
On the other side, certain networks could exhibit strong subjectivity, making it more difficult to determine which chain is the active one. Subjectivity essentially refers to a blockchain network that is susceptible to different interpretations. primarily because a “social network” that depends on node interaction governs their consensus mechanism. Weak subjectivity is required for new nodes (or nodes that have been removed from the network for a long time) to determine which chain is the active one.