Like personal trainers , the Workbooks offer a practical and empathic approach to introductory logic. They are designed for beginners and for anyone who wants to build confidence by doing more exercises. Workbook 3 (Thin Edition) helps you learn how to: do proofs in a Fitch-style natural-deduction system with 11 inference rules (introduction and elimination rules for each connective, reiteration rule). Each inference rule is introduced through numerous exercises : a variety of rule-application exercises, baby-proof exercises, and proof exercises. Their difficulty increases gradually . The point is to train your "logic muscles" until they become strong enough to carry "heavy-weight" content. Visual metaphors help to navigate even multiple subderivations. The study is aided by many examples worked out step by step , warnings of common errors , as well as complete solutions to all exercises. There are two other editions of Workbook 3. The Full Edition has five supplementary units on substitution instances, complex instances of inference rules, proofs of tautologies, additional inference rules, and replacement rules. The Extra Full Edition contains the supplementary units as well as additional exercises. Individual units of Workbook 3 (Extra Full Edition) are available as Logic Self-Taught Workbooklets (3.1, 3.2, etc.). Logic Self-Taught Workbooks are based on the insight that understanding logic is not sufficient for learning logic, just as understanding how to swim is not sufficient for learning to swim and understanding the grammar of a foreign language is not sufficient for learning the language . You need to practice and take an active part in self-teaching . Through systematic work with the Workbooks, you will build self-confidence . You can learn logic, even its hardest parts. ( Previously published as Natural Deduction in Propositional Logic: Workbook 3 Thin Edition by Dr. Phi. ) Contents: Introduction to Natural Deduction: How to Learn Proofs? Unit 3.1 Conjunction Introduction, Conjunction Elimination, and Conditional Elimination Unit 3.2 Biconditional Elimination and Disjunction Introduction Unit 3.3 Subderivation Rules: Conditional Introduction Unit 3.4. Nested Subderivations: Reiteration (R) Unit 3.5. Biconditional Introduction and Disjunction Elimination Unit 3.6. Negation Introduction and Negation Elimination Solutions to Exercises