Modal logic adds two new operators: ◻ -- necessity; and ◇ -- possibility. For example, a triangle's angles necessarily add up to 180, but it's merely a possibil

Modal logic adds two new operators: ◻ -- necessity; and ◇ -- possibility. For example, a triangle's angles necessarily add up to 180, but it's merely a possibility that it will rain tomorrow. That's all there is to it, but things can get very complex when you start adding negations and the other logical connectives.