Logical reasoning PrepTest 145 · Section 4 · Question 20

Incorrect. The conclusion is about determining the possibility of psychic powers. Therefore, an answer about what has already been found doesn't establish that.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Selena Ð I'm psychic!
Figure out if Selna is right → Determine possibility of psychic powers

Answer Anticipation:
This reminds us a bit of that old riddle about the two guardians at the doors, only one of whom can tell the truth . . .

The conclusion here is that if we figure out if Selena is correct, then we can know if psychic powers exist. Selena claims to have psychic powers, which is . . . dubious.

In a question like this, if you're having trouble figuring out the gap, start by considering the possibilities. Here, either Selena is right, or she's wrong. If she's right, then she has psychic powers and it is possible to have psychic powers. After all, to prove something's possible, you only have to show one example of it.

However, what if she's wrong? If she is and she doesn't have psychic powers, then it doesn't prove that it's not possible to have these powers. After all, to show something's impossible, it has to be shown that it never happens and never could.

So the gap in this argument is about the scenario where Selena is wrong. In that case, we need to establish that her one example proves the general rule—that if Selena isn't psychic, then no one is.

Going back to the top, another, more direct route? The argument goes from one example—Selena—to a conclusion about everyone. To get there, it has to be shown that Selena is representative of everyone, and that what's true of her is true of everyone.

Answer Explanation:
This answer plugs the gap in the reasoning. If Selena does have psychic powers, then we know it's possible. If Selena doesn't have psychic powers, and if that's enough to guarantee no one else does, either, then it's not possible to have psychic powers, and the conclusion is justified.

Key Takeaway:
If a sufficient condition in an argument is binary (e.g., here, Selena's claim was either true or false), then it might be worth thinking through what each possibility means to see if that makes clear the gap in the reasoning of the argument.

Incorrect. First, this is more of a necessary premise than a sufficient one in that it establishes it's possible to make a determination the argument calls for, not what that determination is. Second, it's not even necessary—the conclusion is conditioned on being able to determine if Selena's psychic, so it's not assuming that we can determine that.

Incorrect. This answer points out the flaw in the argument—it doesn't fix it!

Incorrect. The argument concludes that determining the truth of Selena's claim is sufficient to establish the possibility of psychic powers—not that it's necessary. This answer is the illegal negation of the conclusion, not a statement that justifies it.