Sufficiency/Necessity Errors In Flaw

Comments

• canihazJD Alum Member Sage ⭐

  December 2020 edited December 2020 8318 karma

  @emmorens said:
  Ok so I am very proficient at identifying these errors in conditional logic, however when they are in abstract terms in the flaw questions it slows me down because I get a little unsure.

  I just took PT 64 and was stuck on the third question which was a mistaken reversal and the correct AC says: "does not present any evidence that the document names every member of the trade group"

  How exactly does that indicate a mistaken reversal? I was stuck on this question for 2 minutes when I had the right answer selected by process of elimination the whole time.

  What are the other common written examples that I should keep an eye out for? I'm looking for common answers or key words to look for that indicate: mistaken negation, mistaken reversal, as well as confusion of necessity versus sufficiency.

  Are there any other than these three that I should be aware of?

  This is one where immediately jumping into conditional logic can hinder you. Just think about what the argument is assuming.

  If you're on the list you're in the group
  B isn't on the list
  So B isn't in the group

  Who said the list was complete?

  Read and extract the argument first then decide what tools you need. We want to be nimble... agile. Assess, don't jump right in. Oh and its 64.3.4.
• FaviPapi-1-1 Member

  December 2020 313 karma

  Hi,

  I think it is the fourth question in section 3 of PT 64, right? Also, the error, if formally said, is not an illegal reversal but an illegal negation.

  Assuming it's that question, I think it's interesting that I didn't think of the error that formally...

  --

  My way:

  I guess, simply said, I just looked at the premise and the conclusion and asked what the argument took for granted or what it neglected to consider... Since the argument in question "seems" pretty good (in other words, the premise does lend some credence to the conclusion), I opted for the latter: what did the argument neglect to consider... As a result, I asked myself, what if the list, even though it was accurate, was not complete? Meaning, what if the list provided to the journalist was missing some names, one of them being Bruch... Would that weaken the argument? Sure.

  --

  JY's way (I just quickly watched the video):

  He is right, you can see this question as an illegal negation; however, I find it too technical, which for me is only ideal for harder questions.

  --
  Illegal Negation:

  P1: If you are working out, then you are running.

  P2: You aren't working out

  C: You aren't running

  Error: Well, just because you failed the sufficient condition of P1 doesn't necessarily mean that you are not running... What if you are not working out but instead trying to get away from a killer who is looking for you, can you run? I hope so!

  Another way you can think of illegal negation is when you are doing logic games. If you fail the sufficient portion of the conditionality, then the rule becomes irrelevant. Similarly, from the example above, we failed the sufficient condition, which is working out, so the rules, or P1, goes away... If that goes away, how can we support the C from just P2? We cannot!

  --

  To your last question, I don't believe there are any other than those three, which are technically the same thing...

  I hope this helps; good luck studying.