LR Problem Set #5, Q 431

[smile22]

In this question, I chose answer D. Sheila states that "people who are driving too fast can easily lose control of their vehicles when they hit a speed bump". I interpret this phrase as saying that, the implementation of Robert's proposal would cause more harm than good, which in my head is Sheila's assumption and answer D.

Why is D wrong and C correct?

[Adam Tyson]

The key to this one is that we are looking for a presupposition, which in our course we more typically call an assumption. What did Sheila have to believe in order for her to make her argument? If her conclusion is true, which of the answers MUST be true?

Your paraphrase of Answer D sounds like an extension of Sheila's conclusion - it may very well be that she thinks the speed bumps would do more harm than good - but is that really what it says? MUST it be true that MOST of the people Robert is concerned about will be harmed? Could it be that only a few will be harmed, maybe just one person? Even if it's as high as 50%, that would still not be MOST people, and yet her argument might still hold water. If I was the only pedestrian hit by an out of control car, I would certainly argue that the speed bumps were a bad idea!

In order for her to believe that speeding drivers will hit the speed bumps and lose control, making them a bad idea, Sheila first has to believe that some people will in fact be speeding when they hit them. To prove Answer C is an assumption of the argument, try the Assumption Negation Technique on it. What would be the impact on her argument if EVERYONE slowed down in the presence of warning signs and speed bumps? Her argument would fall apart completely - there would be no grounds for her claim that Robert's proposal is a bad idea. When the negation of an answer choice destroys the argument, that answer must be an assumption of the argument.

I hope that cleared it up. Good luck, keep up the good work!

[smile22]

That makes complete sense. Thank you for your time.