Ethicist: Every moral action is the keeping of an agreement, and keeping an agreement is nothing more than an act of...

Nicolette on August 25, 2014

question

Can you explain the difference between D and E? I do not understand why D is incorrect. Thanks!

10 Replies

Melody on September 5, 2014

Let's diagram the argument.

"Every moral action is the keeping of an argument,"

P1: MA ==> KA
not KA ==> not MA

"and keeping an agreement is nothing more than an act of securing mutual benefit."

P2: KA ==> ASMB
not ASMB ==> not KA

"Not all instances of agreement-keeping are moral actions."

P3: KA-some-not MA
not MA-some-KA

"Therefore, some acts of securing mutual benefit are not moral actions."

C: ASMB-some-not MA
not MA-some-ASMB

We can combine the P2 ("KA ==> ASMB) and the switched version of P3 ("not MA-some-KA") like so: not MA-some-KA ==> ASMB to conclude: not MA-some-ASMB, i.e. the switched version of the conclusion.

Now, let's diagram answer choice (D).

"All architecture is design,"

P1: A ==> D
not D ==> not A

"all design is art."

P2: D ==> A
not A ==> not D

"not all design is architecture."

P3: D-some-not A
not A-some-D

"Therefore, some art is not design."

C: A-some-not D
not D-some-A

If we were to use the same pattern of reasoning as that in the argument, we would combine P2 (D ==> A) and the switched version of P3 (not A-some-D) like so: not A-some-D ==> A, to conclude: not A-some-A. This is not the conclusion of answer choice (D). Thus, it does not follow the same patter of reasoning.

Let's diagram answer choice (E).

"All books are texts,"

P1: B ==> T
not T ==> not B

"all texts are documents."

P2: T ==> D
not D ==> not T

"not all texts are books."

P3: T-some-not B
not B-some-T

"Therefore, some documents are not books."

C: D-some-not B
not B-some-D

Using the same pattern of reasoning as the argument, we can combine P2 ("T ==> D") and the switched version of P3 ("not B-some-T") like so: not B-some-T ==> D to conclude not B-some-D, i.e. the switched version of the conclusion.

Thus, answer choice (E) uses the same pattern of reasoning as that used in the argument.

Hope that was helpful! Please let us know if you have any other questions.

Angela on January 21, 2017

With timing, I don't foresee myself being able to diagram the question and all of the options out in under 2 minutes. Would you recommend coming back to such questions only at the end?

Mehran on January 29, 2017

@awashing no, we would recommend not worrying about timing initially.

Spend the time to diagram everything as this will dramatically increase your comfort with Sufficient & Necessary conditions. You will eventually get to a point where you can diagram these fast enough.

Remember, Sufficient & Necessary is the most commonly tested form of reasoning that appears on the LSAT, so it is imperative that you know these rules like the back of your hand.

Lastly, it is one minute and 24 seconds per question on average. This means that some questions will take you more time, while other questions will take you less.

Hope that helps! Please let us know if you have any other questions.

Jackie on July 20, 2017

I still don't understand this explanation. They seem identical to me. Help?

Randy on September 3, 2017

The reason why D is incorrect is because the conclusion is stating A-some-not D. When you combine premise 2 and 3 it's stating not A-some ==> A. Which is why it is incorrect. The premise isn't matching up with the conclusion like it should based off the reasoning statement above.

Ashley on July 4, 2018

How do we diagram the second premise?

Mehran on July 5, 2018

@Ashley-Tien, the second premise is diagrammed in a prior post directly above yours on this thread. "And keeping an agreement is nothing more than an act of securing mutual benefit" can be diagrammed as
KA ==> ASMB
(keeping an agreement nothing more than act of securing mutual benefit)

contrapositive: not ASMB ==> not KA

Ryan on May 11 at 12:25PM

how is P3 "not MA"? wouldn't it just be MA? "not all" identifies "some" but how does it negate?

Ravi on May 11 at 04:30PM

@Maybeillgetlucky,

Great question.

P3's sentence is that some agreement keeping is not moral action.

KA - some - not MA

Some statements are reversible, so this can also be written as

not MA - some - KA

Some 'agreement keeping' is 'not moral action.' You're right, this
statement also means that 'Not all agreement keeping is moral action.'
However, this still translates to the same thing, because 'not all'
means 'some.' Saying not all agreement keeping is moral action is the
same thing as saying that some agreement keeping is not moral action.

KA - some - not MA

Does this make sense? Let us know if you have any questions!

Danielle on June 13 at 04:16AM

For a question like this, how do we avoid spending 4+ minutes on the question? Are there a couple answer choices that were easy to eliminate without diagramming? Thank you!