Propositional logic is one of the simplest forms of formal logic. Propositional logic only allows variables (called propositions) such as is_cold and logical operators such as AND and OR. Propositional logic formulae can often be checked by simply craeting a truth table of all the possible Boolean values of the variables. It is not possible to talk about properties of variabes such is_mortal
Used on Chap. 2: page 21