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Argument Validity
- What does it mean for an argument to be valid?
- An argument is valid if its conclusion must be true when the premises are true
Validity from Tautologies
- Modus Ponens → if is true, and is true, then must be true
- Modus Tollens → if and is false, then must be false
- Disjunctive Syllogism → if is true, and is false, then is true
- Transitivity of Implication → if and , then
- (and many more)
Valid Argument
- Premise 1 → if it is raining, then the ground is wet
- Premise 2 → it is raining
- Conclusion → the ground is wet
Invalid Argument
- Premise 1 → if it is raining, then the ground is wet
- Premise 2 → the ground is wet
- Conclusion → it is raining
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