I am confused with q1: when the problem states No Jackson are non-swimmers, the two items we have are /J and /Swimmer, correct? Since no is negating Jacksons? no is a group 4 indicator, so according to the rule I would negate /J as the necessary condition, which gives us /Swimmer → J. Why is this wrong? Or rather, why is the subject J not /J even with the no stated at the beginning of this sentence?

#help So for question 2 he cannot kill both Arya and Sansa, I wrote /S → A, /A→ S, why is this wrong?

I think the Disney argument is the strongest because there are ONLY two ways for Walt to obtain his Genie+ pass that if he is certainly 100% did not fulfill one of the requirements then he absolutely HAS to fulfill the other requirement in order to receive his pass; there is no third possibility whatsoever. In other words, there are no wiggle rooms for doubt in this example. Or, if I'm saying this correctly, fulfilling one of these two requirements is a necessary condition to The tiger example is the second strongest because it is less certain than the Disney argument as it states that not every mammal is suitable to be kept as pet, meaning that there ARE mammals suitable as pets; this argument did not exclude all mammals so one can possibly argue that tigers would fit into the category of mammals that are suitable as pets. The trash bin argument is the weakest because the detective does not have evidence that can be proved beyond a reasonable doubt that the cat caused the mess intentionally (not to mention that intention is often pretty difficult to argue). Again, if I'm saying this correctly, the cat being at the scene licking its paws is necessary but not sufficient to indict its actions.

#feedback Please add subtitles back for this video! I turned cc on but still I didn't see any subtitles for this video

Why can't we contrapose the second conditional to reach the unjustified conclusion?