Q22 - Congenial guests and plentiful

[ManhattanPrepLSAT1]

The argument is way more subtle and actually to some extent less interesting than a lot of these LR questions.

The argument gives us a conditional relationship, tells us that the sufficient condition has been met, and then concludes therefore that the necessary condition follows.

CG + GTE ---> SDP
CG + E
===========
SDP

(Notation Key: CG = congenial guests, GTE = good things to eat, SDP = successful dinner party, E = things to eat)

The flaw in the reasoning is that the sufficient condition has not actually been met. Having plenty to eat is not the same as having plenty of good things to eat. So the conclusion does not follow from the evidence as we have not established that Sylvia had plenty of good things to eat.

(A) is a valid argument and so does not match the flaw.
(B) is a reversal, so is flawed, but does not commit the same flaw.
(C) is a valid argument and so does not match the flaw.
(D) matches the flaw as we do not know that Arnold's meat stock was well-seasoned.
(E) is a negation, so is flawed, but does not commit the same flaw.

[lisahollchang]

Argh! I didn't catch that Sylvia's food wasn't "good" so I thought that the flaw was the "congenial people" didn't necessarily make "congenial guests"!

[WaltGrace1983]

(B) is a reversal, so is flawed, but does not commit the same flaw.

How is (B) a reversal exactly?

It gives us (Bake & Husks On → Moist & Sweet). He wants to "ensure" moist (introducing the necessary condition?) and so he (Bake & Husks On), the sufficient condition. I am a bit confused on how that would be flawed.

[ohthatpatrick]

I think Matt was referring to the
Prem --> Conc
directionality of reasoning
(whereas you're thinking of actual conditional trigger words such as 'ensure')

The argument in (B) is
BECAUSE
he wants moist corn ---> IT'S CERTAIN that he'll bake w/ husks on

So that looks like a reversal of the original conditional.

(B) offers flawed logic. We know that George wants a sure-fire way to get moist corn. But are we CERTAIN he'll do so by baking it in its husk?

No. Baking it in its husk is ONE sufficient way to guarantee moisture, but not necessarily the only way.

Consider this (somewhat dark) analogy:

Lighting your girlfriend's car on fire will ensure that she'll break up with you. Since George wants to ensure that his girlfriend breaks up with him, we can be certain that he will set her car on fire.

Can we be sure of that? There are potentially many other ways he may choose.

So that's the sense in which (B) is reasoning backwards. Let me know if you're still troubled by it.