Wednesday's Challenge

So this is my best guess at the problem that we were struggling with in class on Wednesday.  I’m not sure if I’m using Material Implication correctly, but it seems to work as far as I can tell.  Also, I know that it is in the front cover of the book, but I did not think that we had actually been given MI as a rule of inference yet.  Can anyone point me to when that happened?

1.  ~(PçèQ)                                    Prem. / Therefore: ~(QçèP)

2.  ~[(PèQ) & (QèP)]         1, BE

3.  ~(PèQ) ∨  ~(QèP)         2, DM

           

            4.  QèP                      Supp. CP

            5.  ~(PèQ)                 3,4, DN, DS

6.  (QèP) è~(PèQ)           4-5, CP

7.  ~(QèP) ∨ ~(PèQ)          6, MI

8.  ~[(QèP) & (PèQ)]         7, DM

9.  ~(QçèP)                        8, BE, QED