Abstract

Russell once compared a good notation to a good teacher. Whatever can be said in a good notation can be said in a bad one, just as whatever can be said by a good teacher can be said by a bad one; the difference is that the good notation and the good teacher help one discover more for oneself. It has gradually emerged that the language of modal logic constitutes a good notation for the study of formal provability. That application of modal logic is the subject of George Boolos' welcome new book.