SOLUTION: Phil 10 7. [10] Use indirect proof: / ∴ P ⊃ P

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Question 1195749: Phil 10
7. [10] Use indirect proof:
/ ∴ P ⊃ P
Found 2 solutions by mccravyedwin, Edwin McCravy:
Answer by mccravyedwin(406)   (Show Source): You can put this solution on YOUR website!

/ ∴ P ⊃ P

               |1. ~(P ⊃ P)         Assumption for indirect proof
               |2. ~(~P v P)         1, Material implication     
               |3. ~~P • ~P          2, DeMorgan's law
               |4. P • ~P            3, Double negation
5. P ⊃ P           lines 1-4     Indirect proof

Edwin
Answer by Edwin McCravy(20054)   (Show Source): You can put this solution on YOUR website!

/ ∴ P ⊃ P

               |1. ~(P ⊃ P)         Assumption for indirect proof
               |2. ~(~P v P)         1, Material implication     
               |3. ~~P • ~P          2, DeMorgan's law
               |4. P • ~P            3, Double negation
5. P ⊃ P           lines 1-4     Indirect proof

Edwin
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