I am reading Logic for Dummies... and that should probably end my question answer and existence, but there is a proof in the book that is giving me fits. I've searched

Code:

P -> ~Q, P V R, Q V S, ~R: ~P V S
1. P -> ~Q P
2. P V R P
3. Q V S P
4. ~R P
5. P 2, DS
6. ~Q 1, 5, MP
7. S 3, 6, DS
8. ~P V S 7, ADD

The conclusion is what makes no sense to me. How can you go from P to ~P. Is this a typo in the book, or am I missing something?

Thanks.

I'm going to switch to another book because this is a little to kitschy for me, but I would like to find out if my logic is flawed.