Logical reasoning PrepTest 124 · Section 3 · Question 17

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Cases are like rope, and circumstantial evidence is like strands of the rope. If a few strands are broken, the rope is generally still strong. Therefore, even if a few pieces of evidence are broken, the overall case is still strong.

Answer Anticipation:
This argument provides no reason to believe that a case where some circumstantial evidence has been discredited is just as strong other than the analogy to a rope, where some threads can be cut but the rope remains strong. The assumption here, therefore, is that evidence in a case is similar in all relevant ways to strands in a rope since the argument never establishes that to be the case. Any answer that highlights this incomplete comparison/analogy or a relevant difference between the two situations will serve to highlight the error in reasoning here.

Answer Explanation:
This answer highlights something different about evidence as compared to strands in a rope that calls the analogy into question. If certain pieces of evidence are more crucial to a case than others, then those pieces of evidence being "broken" could weaken the case, as opposed to a rope where the strands are equally strong.

Key Takeaway:
An argument based on a comparison or analogy will often be flawed because the comparison/analogy is unwarranted or incomplete. Similarities and differences can affect these arguments. Usually, the correct answer should be sure to bring up a comparison between the two elements being compared, but sometimes that comparison is implied. Here, for example, there's no premise establishing that all rope strands are equally strong—but it's implied because of the language used and what we know about ropes.

Incorrect. The argument treats the pieces of evidence as adding to each other to make up the case's strength, so it doesn't assume that the case is less than the sum of its parts.

Incorrect. The conclusion only discusses what would happen if "a few" items are discredited—it's unclear at what point the Lawyer would agree that the case is weakened by evidence being discredited. It may be at the point where "many" items of evidence are discredited, so she doesn't fail to consider this possibility.

Incorrect. Close! However, the Lawyer does establish that there are some similarities. She just doesn't establish that they're similar in all relevant ways.

Incorrect. This answer describes a circular argument, but the conclusion here is different from each of the premises, so this answer is incorrect.