• britt
    1
    Hello and thank you for reading. I have been working on this problem and am still stuck. The trick is to use both indirect proof and conditional proof. Any help is appreciated, thank you!

    1. F --> [ ( C --> C ) --> G ]
    2. G --> { [ H --> ( E --> H ) ] --> ( K * ~ K ) } / ~ F

    Code:
    --> means horse-shoe or conditional
    * means dot or and
    ~ means tilde, or negation

    THANK YOU!
  • MetaphysicsNow
    311
    1 1) F --> [ ( C --> C ) --> G ] Premise
    2 2) G --> { [ H --> ( E --> H ) ] --> ( K * ~ K ) } Premise
    3 3) F Assumption
    1,3 4) ( C --> C ) --> G 1,3, Modus Ponens (MP)
    5 5) C Assumption
    6) C->C 5, Conditional Introduction (CI)
    1,3 7) G 4,6 MP
    1,2,3 8) [ H --> ( E --> H ) ] --> ( K * ~ K ) 2, 7 MP
    9 9) E Assumption
    10 10) H Assumption
    10 11) E-->H 9,10 CI
    12) H --> (E-->H) 10,11 CI
    1,2,3 13) K & -K 8,12 MP
    1,2 14) -F 3,13 Law of Non Contradiction

    That gives you an indirect proof of -F given the two premises.

    If by conditional proof, you mean simply prove that if premises 1 and 2 hold, then -F follows, then you can presumably just add the following steps
    1,2 15) (F --> [ ( C --> C ) --> G ]) & (G --> { [ H --> ( E --> H ) ] --> ( K * ~ K ) } ) 1,2 Conjunction Int
    16) [ (F --> [ ( C --> C ) --> G ]) & (G --> { [ H --> ( E --> H ) ] --> ( K * ~ K ) } )] --> -F 14,15 CI
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