 In discussing principles for knowledge, it may be that some of the four above seem acceptable, while others do not: One may disagree with the acceptability of B and 4, say, while accepting K and T. In understanding the relationship between S5 and equivalence relations, a more fine-grained perspective is beneficial: Theorem 1 may be chopped into smaller pieces reflecting the contribution of the individual principles K, T, 4 and B to the equivalence requirementi.e., that the relation should be at the same time reflexive, symmetric and transitive.