While modal logic uses symbols to represent such operators as necessity (a square ) and possibility (a diamond ♢) in the expression of modal statements, I avoid the use of symbolism here, given ...

Possible Worlds: An Introduction to Logic and Its Philosophy by Raymond Bradley and Norman Swartz. An excellent introduction to logic (in all possible worlds), September 24, 2002, by Dr. Lee D.

Modal Reasoning: The study of logic that incorporates modalities—such as necessity, possibility, and knowledge—to characterise different states or conditions.