PT77.S4.Q20 - selena claims to have psychic powers

Comments

• Nicole Hopkins Alum Inactive Sage Inactive ⭐

  January 2016 4344 karma

  @joshgra92 said:
  I don't understand this question. Help please someone.
  

  Video explanations will be up soon
• 1 Like

  quinnxzhang Member

  January 2016 611 karma

  Merging the first sentence into the antecedent, the argument consists of no premises and a single conclusion: if we find out whether Selena has psychic powers, we will determine whether it's possible to have psychic powers.
  
  This seems very counterintuitive. Sure, if we determine that Selena does have psychic powers, then we'll have determined that psychic powers are possible. But if we determine that Selena doesn't have psychic powers, how will we have determined that psychic powers are not possible? Can't it be the case that someone else besides Selena has psychic powers?
  
  In order to rule out this scenario, answer choice (B) says that if it's possible to have psychic powers, then Selena has them. So if we determine that Selena doesn't have psychic powers, the contrapositive of (B) (alternatively, modus tollens) allows us to conclude that it's not possible to have psychic powers.
  
  Thus, by assuming (B), the conclusion in the stimulus is valid. If we determine Selena does have psychic powers, then clearly psychic powers are possible. And by assuming (B), if we determine Selena doesn't have psychic powers, then psychic powers aren't possible.
• Ganbatte Alum Member

  September 2016 40 karma

  the author assumes that Selena is sufficient evidence to indicate possibility, (that she is not an outlier of sort). Just by showing Selena's case, it is enough to prove the possibility.
  
  But the author never makes this assumption explicit. And that's what we should do.
  
  So if she has powers, then it is good enough evidence to make the conclusion that it is possible.
  If she doesn't have powers, then is it good enough evidence to make the conclusion that power is possible still?
  
  Well, what if she is an outlier? That even though she doesn't have power, Professor X nonetheless has power and that proves the possibility of having powers? This is the gap. The author doesn't think this can happen.
  
  That if she doesn't have powers, then it's impossible to have powers.
  Or
  if it is possible to have powers, then Selena has them!