Self-study
Support Investigators have not proved that the forest fire was started by campers. ███ ████ ████ ██████ ████ █████████ █████████ ███ █████ ██ ███ █████████████ ████ ███ ██████ ████ ███ █████ ███ ██████ ██ ███████ ██ ██████████
Method of Reasoning
Investigators haven’t proven that the forest fire was started by campers, and they also haven’t proven that the fire was started by lightning. So the author concludes that investigators haven’t proven that the fire was started by either campers or lightning.
Identify and Describe Flaw
This is a subtle flaw! In concluding that investigators haven’t proven that campers or lightning started the fire, the author overlooks one possibility: even if the investigators haven’t proven that campers started the fire and they haven’t proven that lightning started the fire, it’s possible that they’ve used process of elimination to prove that nothing else could have started the fire. In that case, investigators could have concluded that either campers or lightning started the fire, even if they haven’t been able to prove which of those two suspects was the culprit.
14.
The flawed pattern of reasoning ██ █████ ███ ██ ███ █████████ █████████ ████ ███████ █████████ ███ ██████ ███████ ██ █████████ ██ ███ ████████ ██████
a
Kim has no ██████ ██ ███████ ████ ████ ████ ███ ███ █████████ ███ ████ ███ ██ ██████ ██ ███████ ████ █████ ████ ███ ███ █████████ ██ ███ ███ ██ ██████ ██ ███████ ████ ██████ ████ ██ █████ ████ ███ ███ █████████
Kim has no reason to believe that Sada will win the election, and she also has no reason to believe that Brown will win the election. So the author concludes that Kim has no reason to believe either Sada or Brown will win the election. As in the stimulus, the author here overlooks one possibility: it’s possible that Kim has reason to believe that no one else will win the election (maybe no one else is running), in which case she has reason to believe that the winner will be either Sada or Brown!
b
We have no █████ ██████ ███ ███ ██████ ████ ███ █████ ███████ ███████ ███ ████ ██ ███ ███████ ██ ███ ███ ██████ ████ ███ █████ ███████ ███████ ███ ███████ ██████████ ███ ██████ ██ ██ █████████ ██ ███ ██████
Wrong flaw. The conclusion here isn’t valid—maybe there’s no proof of either theory, but one of the options could still be less plausible! What if the vent in the ceiling isn’t big enough for a person to get through, or the window is 100 stories up? But that’s not the flaw from the stimulus: here, the conclusion is that both options are equally possible; in the stimulus, the conclusion is that there’s no proof that the truth lies in one of the two options presented.
c
Most of the ████████ ██ ██ █████████ ███ ███████████ ███████ ███ ████ ██ ███ ████████ ██ ██ █████████ ███ ████ ███ ██ █████ ██ ████ ██ ███ ███████████ ██████ ██ ██ █████████ ███ ████ ███ ██ █████
Wrong flaw. This argument relies on a misunderstanding of the quantifier “most.” Let’s say there are 100 students in the author’s dorm: 51 are engineering majors and 51 are from out of town. One student must be both an engineering major and from out of town, but the others could fall into only one of those two categories! In that case, most of the engineering majors aren’t from out of town. But this isn’t the same flaw we saw in the stimulus, where the premises don’t include “most” relationships.
d
In some parts ██ ███ ██████ ███████ ██ ██████████ █████ ███████ ██ █████████ ██ ████ █████ ██ ███ ███████ ██ █████ ███ ████ █████ ██ ███ ██████ ██ █████ ████ ███████ ███ ███████ ███ ██████████
Wrong flaw. The parts of the forest where camping is permitted could be completely separate from the parts where hunting is permitted! But this isn’t the flaw from the stimulus, where the premises don’t include “some” relationships.
e
The evidence shows ████ ███ ███ █████ ████ ████ ██████ ██ █████ ██ ███ ████ ██ ███ █████████ ████████ ██ ████ █████ ████ ██ █████ ████ ████ ██████ ██ ██████████ ██ ███ ████ ██ ███ █████████ ██████████ ███ ████████ █████ ████ ███ ███ █████ ████ ████ ██████ ██ ████ █████ ███ ██████████ ██ ███ ████ ██ ███ █████████
Wrong flaw. Just because the car could’ve been driven by Jones or Katsarakis doesn’t mean they both could’ve driven the car! How would that even work? Regardless, this isn’t the flaw from the stimulus—the stimulus concludes that there’s no evidence that the truth lies in one of the two options presented, whereas (E) concludes that both options could be true simultaneously.