Question about conditional logic section in LR book

[zainrizvi]

Great book guys.

Quick question about the "Linking Assumptions" section p.365. So within the example given, it is stated that the assumption "required" is everyone who buys ice cream is rich... but that doesn't HAVE to be true.... what if every child who likes ice cream is rich. Now the conclusion (every child is rich) makes sense.... although the intermediate conclusion is just an irrelevant piece of detail.

Just wondering if this makes sense.. I know we try to make the premise fit the conclusion, but it doesn't have to entail all the premises right? Or do we typically do that on the LSAT....

The real necessary assumption is that SOME people who buy ice cream are rich, not ANY people who buy ice cream are rich.

[rinagoldfield]

Hi Zainrizvi,

Sharp and sophisticated question!

Here’s the argument you’re talking about (it’s on p. 353 in my edition):

Child --> likes ice cream --> buys ice cream
therefore
Child --> rich

The most obvious assumption here is buys ice cream --> rich.

You’re right that this assumption is sufficient but not necessary, since likes ice cream --> rich would also get us to the conclusion.

Likes ice cream --> rich doesn’t imply likes ice cream --> buys ice cream --> rich; this would be faulty chaining.

Likes ice cream --> rich is similarly sufficient but not necessary, since child --> rich could also get us to the conclusion.

I’ve yet to encounter an LSAT problem that plays this trick, however. All the problems I’ve seen that have conditional logic chains focus on the terms just on either side of the gap.