In this case, any formula K is intermediate between A and B. More generally, if A and B are two PL formulas, B is a logical consequence of A, and A and B are not logically equivalent, K $\stackrel{def}{=}$ (x $\land$ A) $\lor$ ($\neg$ x $\land$ B) is intermediate between A and B for a propositional letter x not occurring in both A and B. Indeed, it is A $\Rightarrow$ K, K $\Rightarrow$ B, but K ha