(January 1, 2022 at 11:37 pm)LadyForCamus Wrote: I wasn’t exactly sure which sub forum to put this in.
Which formal structural error is this? Is it still considered Affirming the Consequent if they’re using negations of p and q in the second premise?
The argument form
!p -> !q
q
------
p
is valid. In fact, !p->!q is logically equivalent (contrapositive) to q->p. Then, with q, we can, in fact, conclude p.
The problem, as others have pointed out, is the assumption that !p->!q. This is what makes the argument unsound.