# Teacher to a student: You agree that it is bad to break promises. But when we speak to each other we all make an ...

Joseph on April 25, 2016

Why D and not E?

I eliminated all of the answers except D and E for this one. Why is D the correct answer and E isn't?

Mehran on May 12, 2016

@Joseph let's take a closer look.

The conclusion of the teacher's argument is, "So even if you promised Jeanne that you would tell me she is home sick, you should not tell me that, if you know that she is well."

The support provided for this conclusion?

P1: "You agree that it is bad to break promises."

P2: "But when we speak to each other we all make an implicit promise to tell the truth, and lying is the breaking of that promise."

Notice the flaw here. P1 sets forth that it is bad to break promises but there are two promises here and, no matter what, one will be broken.

The student promised Jeanne that she would tell the teacher that she is home sick and if she doesn't, that would also be a broken promise.

Why is it that this implicit promise to tell the truth when speaking to someone else is more important than the explicit promise the student made to Jeanne?

This is a Strengthen with Necessary Premise question so we are looking for the answer choice that not only strengthens but that is also necessary to the argument.

(D) states, "Some implicit promises are worse to break than some explicit ones."

This clearly strengthens by giving us a reason to prefer breaking the explicit promise to Jeanne.

Now let's negate to make sure that it is also necessary to this argument.

The negation of (D) is, "No implicit promises are worse to break than some explicit ones."

This would destroy the argument (i.e. breaking an implicit promise is always better than breaking an explicit promise), so (D) is the correct answer.

Let's check (E) though just to see the difference. E states, "One should never break a promise."

Notice that (E) does not even strengthen the argument since we have two promises here and, no matter what, one will be broken.

Hope this helps! Please let us know if you have any other questions.