This document discusses propositional logic and knowledge representation. It introduces propositional logic as the simplest form of logic that uses symbols to represent facts that can then be joined by logical connectives like AND and OR. Truth tables are presented as a way to determine the truth value of propositions connected by these logical operators. The document also discusses concepts like models of formulas, satisfiable and valid formulas, and rules of inference like modus ponens and disjunctive syllogism that allow deducing new facts from initial propositions. Examples are provided to illustrate each concept.