ABSTRACT
In the last chapter we introduced canonical models for normal modal systems and used them to prove the completeness of the systems we had been studying in Part I. As we remarked there there are many more normal modal systems, and in this part of the book we shall have a look at some of them with a view to illustrating some general techniques and properties of them. This chapter will be concerned to look at some features of canonical models. We first introduce three other systems: S4.3, S4M and S4.2, and include completeness proofs for them using canonical models. We shall then look at the structure of the frames of canonical models for a selection of systems, and finally we will discuss some limitations of the canonical model technique for proving completeness by looking at a system where the frame of its canonical model does not validate all its theorems.
