I'm stuck on how to progress with this proof, despite I have tried, I cannot see the next move.
Given this proof without predicate:
So far what I've accomplished:
My idea is, as I can't see any other option using (-(Sv(P->Q))
as the first assumption in order to introduce a conditional, so the assumption must end in P ^ -Q ^ -S
. As you can see I have obatined -Q and -S
but, how do I proof P
?