Introduction to Logic

Overview

Instructor: Mark Thor's Bay
Course covers basics of:
- Categorical logic
- Propositional logic
- Predicate logic
Current focus: Basic concepts
- Validity, truth, soundness, strength, and cogency

Core concept in logic
Focus on testing for the validity of arguments
Distinction between deductive and inductive reasoning
- Deductive reasoning: Reasoning by necessity (certainty)
- Inductive reasoning: Reasoning by probability (uncertainty)

Valid Argument: Impossible for conclusion to be false if premises are true
Invalid Argument: Possible for conclusion to be false even if premises are true
Validity is dependent on the form of the argument
Sound Argument: Valid form with true premises
Unsound Argument: Valid form but false premises; or automatically unsound if invalid
Examples:
- Valid: All TV networks are media companies; NBC is a TV network; hence, NBC is a media company
- Invalid: All banks are financial institutions; Wells Fargo is a financial institution; hence, Wells Fargo is a bank

Based on probability
Strong Argument: Improbable that the conclusion is false if premises are true
Weak Argument: Conclusion does not probably follow from the premises
Cogent Argument: Strong argument with true premises
Uncogent Argument: Strong form but false premises, or weak argument
Examples:
- Strong: All dinosaur bones found have been over 50 million years old; future finds likely will be too
- Weak: Don Perignon is expensive; Marquis de la Tour is also French; therefore, it is expensive

Goal: To cultivate the ability to distinguish sound from unsound arguments in everyday life
Exercises in textbook provide practice in evaluating arguments