ABSTRACT
In this and the following chapters, the difficulties of quantified modallogic will be discussed. As the seemingly queer results we have to accept vary from system to system, it will be helpful to remember that each of the five Lewis systems SI-S5 is stronger than the preceding one, and that Gödel's basic system, Fey's system T, and von Wright's system Mare all equivalent, stronger than S2, weaker than S4, incomparable with S3. In the Gödel-Feys-von Wright system and all stronger systems, if rp is provable, so is rO<pl 1 Let us call this rule 'RL'.
