Section8.5-8.7

Section8.5-8.7 - A D D Therefore: A Argument form: p q q...

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Section8.5-8.7 Review: Argument written out- substitution instances for kinds of argument forms that are written in lower case letter Argument written in symbols Argument forms can match different arguments; arguments can have more than one argument form that it could substitute into Every argument form either valid or invalid 1. An argument form is invalid if and only if it has at least one substitution instance with all true premises and a false conclusion 2. An argument form is valid if and only if it has NO substitution instance with all true premises and a false conclusion p1: If JFK was assassinated, then JFK is dead p2: JFK is dead C: JFK was assassinated Invalid argument A D D Therefore: A P1: if Reagan was assassinated, then Reagan’s dead P2: Reagan is dead C: Reagan was assassinated Here’s why argument before was invalid and this was invalid
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Unformatted text preview: A D D Therefore: A Argument form: p q q therefore: p (specific argument) Could also be: p q therefore: r Argument invalid because its argument form is invalid Truth table to test validity/invalidity p q p q T T T T F F F T T F F T Conclusion P2 P1 Line 3 makes argument invalid It has two true premises and a false conclusion!! Pay attention to what is the premises and what is the conclusion All it takes is one invalid interpretation (one of the substitution instances) to make the entire thing corrupt When it is a valid argument form, anything with that specific substitution instance will be a valid argument For example: p q p therefore:q is a valid argument form P p q q T T T T F F F T T F F T P1 P2 Conclusion Only invalid when it has two true premises and a false conclusion, not any other way!!!!...
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Section8.5-8.7 - A D D Therefore: A Argument form: p q q...

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