Logical Reasoning

PT113 · S2 · Q3 Joan got A’s on all

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Joan got A’s on all her homework assignments, so if she had gotten an A on her term paper, she could pass the course even without doing the class presentation.

Conclusion (so it is obvious that)

Joan will have to do the class presentation to pass the course.

Evidence

If Joan had gotten an A on her term paper, she could pass the course without doing the class presentation.

But she didn't get an A on her term paper.

Evaluate

Whenever we're doing Flaw and we see any Conditional Logic, we should immediately be suspicious that the argument is going to commit an illegal negation or reversal (aka, the #1 Famous Flaw, Necessary vs. Sufficient).

The first sentence has a conditional rule, signified by if.

If A on term paper, then pass without presentation.

So an illegal reversal would sound like,

An illegal negation would sound like,

And that second thing is exactly what the argument did!

Goal

We can describe this flaw formally as confusing Necessary and Sufficient conditions. We were told in the evidence that getting an A on her term paper would have been sufficient to get Joan out of having to do the class presentation.

But the author is acting like it's necessary. He's acting like if she didn't get the A then she must do the class presentation.

We can describe the flaw conversationally by saying, (a doctor's note / extra credit / a bribe or threat from her parents / etc.)

3.

The argument's reasoning is questionable because the argument

  1. ignores the possibility that Joan

    Wrong Prefix: objection vs. assumption

    This author takes for granted / presumes that Joan has to either get an A on her term paper or do the class presentation. So this answer would be correct if it began with any of the assumption prefixes. It doesn't fail to consider / ignore the possibility that she has to get an A or do the class presentation. The former are prefixes that indicate what the author was thinking or assuming. The latter are prefixes that raise a potential objection to the argument. When we see fails to consider / overlooks the possibility that X, we ask ourselves if X would weaken. Would it hurt the argument if we said, "Hey, author -- Joan has to either get an A on her term paper or do the class presentation to pass the course"? Definitely not. That completely matches the author's thinking.

    7% picked this

  2. Correct

    presupposes without justification that Joan’s

    Why this is right

    Since this answer starts with takes for granted / presumes / presupposes that X, we can just ask ourselves, "Was the author assuming X?" Did this author assume that Joan's not getting an A on the term paper prevents her from passing the course without doing the class presentation? Yes! That perfectly matches the reasoning move. The author establishes that Joan didn't get an A, and then moves from that idea to the conclusion that she will have to do the class presentation in order to pass the course. If we negated this assumption (not getting an A doesn't prevent Joan from passing without doing the class presentation), would that weaken? Totally! This author thinks she has to do the class presentation in order to pass, but this negation would be saying the opposite. Why is it bad for the author to be assuming that not getting an A prevents Joan from passing the course without doing the class presentation? Because we were never told that passing the course w/o doing the class presentation was dependent on getting an A. We know that getting an A is one potential way that you can pass the course without doing the class presentation (sufficient). But we were never told it's the only way to pass the course without doing the class presentation (necessary), as the author seems to be thinking.

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

    82% picked this

  3. overlooks the importance of class

    Trap

    Not an Objection Out of Scope: overall course grade Nothing in the argument has anything to do with her overall course grade, so this feels out of scope. Since the answer begins with fails to consider / overlooks the possibility that X, we want to ask ourselves if X could weaken. Here, X isn't expressed as a clause but rather as a long phrase. Still we could turn it into a clause. We can ask ourselves, "Would it hurt the author's argument if we said Hey, author -- class presentations are very important to a student's overall grade". No, that wouldn't hurt the argument at all. The author was never talking about overall grade nor was she assuming anything about whether class presentations have or don't have an important connection to overall grade.

    2% picked this

  4. ignores the possibility that if

    Doesn't Ignore

    Like (A), this answer is pairing up something the author thinks with the prefix fails to consider / ignores the possibility. The author's premise says, If get A on term paper, then don't need to do CP by contrapositive that means, if do need to do CP, then didn't get A on term paper Those two things mean the same thing. A conditional and its contrapositive have the same meaning, just like "X is bigger than Y" has the same meaning as "Y is smaller than X". So the author's premise said "X > Y" and this answer is saying the author ignored the possibility that "Y < X". The author announced that possibility; she didn't ignore it.

    4% picked this

  5. fails to take into account

    Not an Objection

    Since this answer starts with fails to consider / ignores the possibility that X, we can just ask ourselves, "Does X weaken?" Can we object to this argument by saying, "Yo, author -- some students get A's on their term paper but don't pass the course"? Nope. The author's argument is about someone who didn't get an A on their term paper, so whatever is true of people who do get an A on their term paper is irrelevant to this conversation about Joan's situation.

    5% picked this

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