The course is organized into three chapters. The first describes classical propositional logic (also known as Boolean logic), that of "true" and "false", interpretable by truth tables. The second focuses on first-order theories, extensions of classical logic, where we address the question of quantifiers and associated grammar rules. The example of Peano arithmetic is treated centrally, and Gödel's incompleteness theorems are explained. Finally, the last chapter develops a formal set theory. All the traditional concepts (union, parts, relation, function, Cartesian product, etc.) are reviewed, and the theory of ordinals and cardinals is studied in detail. The axiom of choice and the axiom of regularity are also studied.