Abstract:
Since I started to study modal logic, the canonical models which supply a large number of completeness results have been centred on my interest in logic. Contrary to a fact that they look simple at first sight, their nature is complex so that we need strong tools in order to investigate it.
The tools we shall treat in this thesis were exploited by many authors, e.g., K. Fine, S.K. Thomason, R.I. Goldblatt and van Benthem and require prerequisites on universal algebra and model theory. We shall only make simple comments on these subjects, so for the details reader should refer to the books listed in references in the end of the thesis.
