LSAT Explanation PT 30, S2, Q11: Teacher to a student: You agree

LSAT Question Stem

Which one of the following is an assumption on which the teacher's argument depends? 

Logical Reasoning Question Type

This is a Necessary Assumption 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 teacher is talking to a student and presents the following argument:

Premise 1: It is bad to break promises.

Premise 2: When we speak to each other, we make an implicit promise to tell the truth.

Conclusion: You should not tell the teacher that Jeanne is home sick if you know she is well, even if you promised Jeanne that you would say so.

The structure of the argument is that breaking promises is bad, and lying is considered breaking an implicit promise to tell the truth. Therefore, the student should not lie about Jeanne's situation. However, there is a missing piece of information in this argument, which leads us to an "Evaluate" question: "Which promise should the student prioritize: the implicit promise to tell the truth or the explicit promise made to Jeanne?"

Now let's discuss the question type and the answer choices. This is a Necessary Assumption question, which asks us to identify an assumption on which the teacher's argument depends.

a) Most people always tell the truth.

This answer choice is out of scope because the argument is not concerned with what most people do.

b) It is sometimes better to act in a friend's best interests than to keep a promise to that friend.

This answer choice is tempting but ultimately out of scope because the argument is not about acting in a friend's best interests.

c) Breaking a promise leads to worse consequences than does telling a lie.

This answer choice is out of scope because it focuses on consequences, which are not discussed in the argument. Additionally, it is important to remember that lying is considered breaking an implicit promise, so this choice is somewhat incoherent.

d) Some implicit promises are worse to break than some explicit ones.

This is the correct answer. The teacher's argument depends on the assumption that breaking the implicit promise to tell the truth is worse than breaking the explicit promise made to Jeanne. If this assumption were not true, the argument would not hold.

e) One should never break a promise.

This answer choice may seem tempting, but it is incorrect because it would create a contradiction in the argument. If one should never break a promise, then the student should not break their promise to Jeanne, which goes against the conclusion of the argument.

In conclusion, the correct answer is D, as the teacher's argument depends on the assumption that some implicit promises (such as telling the truth) are worse to break than some explicit promises (like the one made to Jeanne).