Advice on Modal Logic

Abstract

Everyone knows how much more pleasant it is to give advice than to take it. Everyone knows how little heed is taken of all the good advice he has to offer. Nevertheless, this knowledge seldom restrains anyone, least of all the present author. He has been noting the confusions, misdirections of emphasis, and duplications of effort current in studies of modal logic and is, by now, anxious to disseminate all kinds of valuable advice on the subject. Thus he is very happy that the Irving meeting has provided such a suitable and timely forum and hopes that all this advice can provoke some useful discussion --- at least in self-defense. The time really seems to be ripe for a fruitful development of modal logic, if only we take care to purify and simplify the foundations. A quite flexible framework is indeed possible: the old puzzles can be brushed aside, and one can begin to provide meaningful applications.