In propositional logic, we can let p stand for “Roses are red” and q stand for “Violets are blue”. Then p ∧ q will stand for “Roses are red and violets are blue”. But we lose a lot in the translation into logic. Since propositional logic only deals with truth values, there’s nothing we can do with p and q in propositional logic that has anything to do with roses, violets, or colour. To apply logic to such things, we need predicates. The type of logic that uses predicates is called predicate logic or, when the emphasis is on manipulating and reasoning with predicates, predicate calculus.