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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 โ if is true, and is true, then must be true
- Modus Tollens โ if and is false, then must be false
- Disjunctive Syllogism โ if is true, and is false, then is true
- Transitivity of Implication โ if and , then
- (and many more)
Valid Argument
- Premise 1 โ if it is raining, then the ground is wet
- Premise 2 โ it is raining
- Conclusion โ the ground is wet
Invalid Argument
- Premise 1 โ if it is raining, then the ground is wet
- Premise 2 โ the ground is wet
- Conclusion โ it is raining
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