 Logics may be stronger or weaker than each other, and knowing the frame properties of their axioms may help us to understand their relationship. For example, as 4 is derivable from \(\{\text{K},\text{T},\text{5}\}\), all the theorems of S4 are derivable in S5. S5 is thus at least as strong as S4. In fact, S5 is also strictly stronger: It can prove things which S4 cannot.