Classical logic is usually viewed as a masterpiece of the human mind. It serves as the basic logic of classical mathematics and almost all other sciences. However, despite its long history and venerable reputation, it is not an ideal logic. It faces serious objections which demonstrate that as a practical tool, it is inadequate. A logic is an inadequate tool if its practical use generates counterintuitive and absurd situations that are highly incompatible with common sense and natural language. Classical logic and its modal extensions that we studied in the preceding chapter are just such logics. A few examples will suffice to prove the point.