Weak Subjectivity

The necessity for some nodes to rely on other nodes to pinpoint which is the active chain in a Proof-of-Stake blockchain.

When a node is disconnected from a network for a long time and comes back online, weak subjectivity is required to allow it to make a decision about which is the active chain.

This concept comes into play in networks whose consensus mechanisms feature a strong social element. New and reactivated nodes need a little time to figure out and synchronize to the valid state of the system.