Q23 - If the prosecutor wanted to charge Frank with embezzle

[smiller]

Question Type:
Match the Flaw

Stimulus Breakdown:
Premise:
1. prosecutor wanted to charge → Frank already indicted
2. ~ Frank already indicted

Conclusion:
~ Frank embezzler


Answer Anticipation:
This argument is based on conditional logic, and we might expect a common conditional logic flaw (invalid reversal/invalid negation). However, that's not where the flaw lies. The premise is about the prosecutor wanting to charge Frank with embezzlement, but the conclusion is about whether or not Frank actually is an embezzler. We're looking for an answer that displays this same kind of shift.

Correct Answer:
(C)

Answer Choice Analysis:
(A) This contains an invalid reversal. It's not the same flaw as the stimulus.

(B) This contains an invalid negation. That flaw doesn't appear in the stimulus.

(C) This is the correct answer. We have a shift from a premise about Makoto believing that he left the oven turned on, to a conclusion about him definitely not leaving the oven turned on.

(D) This contains an invalid reversal. That flaw doesn't appear in the stimulus.

(E) The second premise and conclusion do not match the stimulus. We can diagram the stimulus this way:
A → B
~B
Therefore, ~C

Choice (E) gives us
A → B
C
Therefore, B

Takeaway/Pattern: To answer a Match the Flaw question correctly you must take time to understand the exact flaw in the stimulus. Incorrect answer choices will often have a similar structure, but a different flaw.

#officialexplanation

[sarahmahmood01]

I translated this question as follows:

A->B
-B->C

I originally chose answer choice D because they both had a third element (C).

I understood that C is A->B, -B->-A, so I'm unsure as to how this is the correct answer since it lacks the third element being randomly introduced.

Thanks in advance for any help!

[rsmithpt267]

^When reading this, I did not read Frank is not an embezzler as being a 3rd element. I don't know if this is correct but I read it as:

A->B
-B->-A

I also think D is wrong because I think the structure is

A->B
B->A

For it to match, I believe it would have had to say She did NOT come in early, So apparently she is NOT getting a promotion.

[maryadkins]

So there IS a new element introduced in the stimulus—in other words, it's not the same as the first part. Think about it: we have "if the prosecutor wanted to charge Frank with embezzlement" and "Frank is not an embezzler." Are these inverses of the same thing? NO! They're totally different. The prosecutor may want to charge Frank with embezzlement and he may or may not be an embezzler. In other words, it's NOT:

A --> B
~B --> ~A

Rather, as the first poster noted, it's:

A --> B
~B --> C [a new idea]

The correct answer choice, (C), is the same way. Makoto BELIEVING he left the oven on is not the same as the oven actually being on.

Incorrect answer choice (D) has the same problem—her believing she's getting a promotion isn't equivalent to her actually getting one—but it adds an additional flaw, which you noted, rsmithpt267:

A -> B
B --> C

(A) has this same flaw, and (E) would look like this:

A --> B
C --> B

[LenB401]

So there IS a new element introduced in the stimulus—in other words, it's not the same as the first part. Think about it: we have "if the prosecutor wanted to charge Frank with embezzlement" and "Frank is not an embezzler." Are these inverses of the same thing? NO! They're totally different. The prosecutor may want to charge Frank with embezzlement and he may or may not be an embezzler. In other words, it's NOT:

A --> B
~B --> ~A

Rather, as the first poster noted, it's:

A --> B
~B --> C [a new idea]

The correct answer choice, (C), is the same way. Makoto BELIEVING he left the oven on is not the same as the oven actually being on.

Incorrect answer choice (D) has the same problem—her believing she's getting a promotion isn't equivalent to her actually getting one—but it adds an additional flaw, which you noted, rsmithpt267:

A -> B
B --> C

(A) has this same flaw, and (E) would look like this:

A --> B
C --> B

So sorry I'm confused the first LSAT instructor put
A → B
~B
Therefore, ~C

and you put down this

A --> B
~B --> C [a new idea]

Im confused on which diagram is correct as well as what answer choice C looks like in conditional logic form? please help

[ohthatpatrick]

The argument would look like this:

P wanted to charge F with E --> F would be indicted.
F has not been indicted.
----------------------
F is not E

It's a little imprecise to convert them all to two repeating ideas (E / ~E and I / ~I),
but if you want visual simplicity, it's like this:
E --> I.
~I.
----------
~E.


The teacher who showed those last two moves as a conditional was just expressing that the author's argument core was flowing from ~I to ~E.

(C) would look like this:
M believed O is on --> Rush home.
~ Rush home.
-------------------
O is off

Or if we oversimplify and pretend Oven is off/on and do/don't Rush Home:
O on --> Rush.
~Rush.
-------------------
O off


Hope this helps.