Page 2-13, Question 7

[Blueballoon5%]

Hello! I am confused with the answer key explanation for why answer choice (C) is wrong. The answer key states, "This answer concludes that Amanda is generous on the basis of her actions. As discussed previously, there is no way to use the principle to conclude that an individual is generous." Why is this the case? Why can't we make any conclusions about a sufficient condition ("being generous")?

Thanks!!

[Dave Killoran]

Hi Blue,

This is a key point, and one that troubled you on a different question as well. This is true: there's nothing you can add to a conditional premise to force the sufficient condition to happen (nor can you conclude that the necessary didn't happen). In other words, if you are given the following:

• Premise: A B
  
  Conclusion: A

What could you add to make it the conclusion follow and the argument be valid? If you add A, then it's a circular argument (premise and conclusion are identical). If you add B, then no conclusion follows. And if you add Not B then the conclusion is Not A. There are no other choices at that point

Btw, I go into detail about this in the LRB in the Principle section if that's a help.

Thanks!