All poets, aside from those who write only epigrams, have wit. All lyrical composers are poets. Azriel does not write...

Michelle on November 19, 2017

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4 Replies

Mehran on November 20, 2017

Let's take a closer look at the stimulus:

"All poets, aside from those who write only epigrams, have wit."

PR 1: P & not OWE ==> W
not W ==> not P or OWE

"All lyrical composers are poets."

PR 2: LC ==> P
not P ==> not LC

"Azriel does not write epigrams, though he is a lyrical composer."

P1: not OWE, LC

"So Azriel has wit."

C: W

Notice that P1 invokes the sufficient condition of PR 2 (because if you don't write epigrams then you obviously do not write only epigrams), allowing us to conclude P exists, which then allows us to properly conclude W because both sufficient conditions are met, i.e. P & not OWE.

This logical structure is identical to (E), which is the correct answer. Let's break down (E) just to see it clearly.

"All residential buildings are subject to the original fire code, except for those built last year."

PR 1: RB & not BLY ==> OFC
not OFC ==> not RB or BLY

"All townhouses are residential buildings."

PR 2: TH ==> RB
not RB ==> not TH

"Bloom House was not built last year, and it is a townhouse, . . . "

P1: not BLY, TH

" . . . so it is subject to the original fire code."

C: OFC

Notice that P1 invokes the sufficient condition of PR 2, allowing us to conclude RB exists, which then allows us to properly conclude OFC because both sufficient conditions are met, i.e. RB & not BLY.

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

Sadaab on September 3 at 01:17AM

Can you go over choice A?

Irina on September 3 at 05:06PM

@sadaabrahman,

Let's compare the original argument to (A).

(1) p & ~q -> r
(2) s-> p
(3) ~ q & s
(4) r

versus (A)

(1) ST & ~DFC -> SFI
p & ~ q -> r
(2) ST -> PW
p -> s
(3) ~DFC & PW
~q & s
________________
(4) SFI
r

(A) is a flawed argument because the second premise tells us that all squeeze toys are prewrapped:

ST -> PW

The argument commits a logical fallacy, known as affirming the consequent, and concludes that because something is prewrapped, it must be a squeeze toy:

PW -> ST

and if it is a squeeze toy & not designed for cats, it must be safe for infants.

ST & ~DFC - > SFI

This is a valid inference per premise (1) but because PW -> ST inference is invalid, the conclusion is invalid.

The only proper inference from the second premise is:

~ PW -> ~ ST

If smth is not prewrapped, then it is not a squeeze toy.

Does this make sense?

Let me know if you have any further questions.

Sadaab on September 4 at 12:15AM

Thanks Irina!