Modal Logic and Its Applications, Explained Using Puzzles and Examples

1.We shall be concerned, at first, with alethicmodal logic, or modal logic tout court. 2.The starting point, once again, is Aristotle, who was the first to study the relationship between modal statements and their validity. 3.However, the great discussion it enjoyed in the Middle Ages. 4.The official birth date of modal logic is 1921, when Clarence Irving Lewis wrote a famous essay on implication.