You can’t get very far in argument analysis without learning some basic concepts of propositional (also known as “sentential”) logic. In this course I review these basic concepts, but I don’t spend time working out formal proofs in propositional logic (as you would in a course in symbolic logic). My interest here is in presenting and explaining those concepts that are needed for doing ordinary, everyday argument analysis, and in particular those concepts that are used in discussions of formal and informal fallacies. Fallacies are a fun topic and a student favorite, but many fallacies can only be understood if you first understand these basic concepts of propositional logic.
I should point out that if there is one skill that is essential to master for the LSAT (the Law School Admission Test), it’s the ability to reason with conditionals (statements of the form “If A then B”). This topic is covered thoroughly in Part 4 of this course.
Introduction (5:56) (FREE)
Part 1: Compound Claims
1.1 Conjunctions (A and B) (2:23)
1.2 Disjunctions (A or B) (3:54)
1.3 Conditionals (If A then B) (7:02) (FREE)
Part 2: Contradiction and Consistency
2.1 Contradictories (not-A) (2:34)
2.2 Contradictories vs. contraries (3:04)
2.3 Contradictions (A and not-A) (3:50)
2.4 Consistent vs. inconsistent sets of claims (5:04) (FREE)
Part 3: Contradictories of Compound Claims
3.1 not-(not-A) (2:19)
3.2 not-(A and B) (2:57)
3.3 not-(A or B) (1:51)
3.4 not-(If A then B) (3:47) (FREE)
Part 4: Ways of Saying “If A then B”
4.1 A if B (2:49)
4.2 A only if B (3:34) (FREE)
4.3 A if and only if B (2:28)
4.4 A unless B (2:00)
4.5 The contrapositive: If not-B then not-A (3:24) (FREE)
4.6 (not-A) or B (4:35)
4.7 Necessary and sufficient (4:42)
Appendix: Categorical Claims and Their Contradictories
1. Categorical vs propositional logic (5:47) (FREE)
2. All A are B (3:06)
3. Some A are B (3:17)
4. Only A are B (3:23) (FREE)
5. Square of opposition (1:00)
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