LSAT Explanation PT 35, S4, Q13: Mayor: The law prohibiting pedestrians from

LSAT Question Stem

The mayor's argument is flawed because it 

Logical Reasoning Question Type

This is a Flaw question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

First, let's analyze the argument in the passage. The mayor claims that the law prohibiting pedestrians from crossing against red lights serves no useful purpose. The mayor's reasoning is that a useful law must deter the kind of behavior it prohibits, and this law does not do that. The mayor then discusses two groups of pedestrians: those who always violate the law and those who never do. The mayor argues that the law is not useful for either group. This argument can be broken down into the following structure:

Premise 1: A useful law must deter the kind of behavior it prohibits.

Premise 2: The law does not deter pedestrians who always violate it.

Premise 3: The law is not needed for pedestrians who never violate it.

Conclusion: The law serves no useful purpose.

The question type for this problem is a Flaw question, which asks us to identify the flaw in the mayor's argument.

Now, let's evaluate the answer choices:

a) The mayor's argument does not rely on the assumption that most automobile drivers will obey the law prohibiting them from driving through red lights. This answer choice is not relevant to the mayor's argument and can be eliminated.

b) The mayor does not use the word "law" in different senses in the premises and conclusion. The word "law" is consistently used to refer to the law prohibiting pedestrians from crossing against red lights. This answer choice is incorrect.

c) The possibility that a law might not serve a useful purpose even if it does deter the kind of behavior it prohibits is not the flaw in the mayor's argument. The mayor's argument is based on the idea that the law does not deter the behavior it prohibits. This answer choice is incorrect.

d) This answer choice correctly identifies the flaw in the mayor's argument. The mayor fails to consider whether the law ever dissuades people who sometimes but not always cross against red lights. By only discussing two extreme groups of pedestrians (those who always violate the law and those who never do), the mayor ignores the possibility that the law might serve a useful purpose for people who fall in between these two extremes. This is the correct answer.

e) The mayor's argument does not rely on the assumption that crossing against red lights is more dangerous than crossing on green lights. The argument is focused on whether the law deters the behavior it prohibits, not on the relative dangers of crossing against red lights. This answer choice is incorrect.

In summary, the correct answer is D, as the mayor's argument is flawed because it fails to consider whether the law ever dissuades people who sometimes but not always cross against red lights.