LSAT 138 | Section 2 | Logical Reasoning: Q18

QUESTION TEXT: Every delegate to the convention is a party member…

QUESTION TYPE: Must Be True

FACTS:

1. Delegates ➞ Party Member
2. Delegates SOME government official
3. Government Official ➞ Speaker

ANALYSIS: We know that all delegates are party members. And some delegates are officials.

Let’s say that in fact, 5 delegates are officials. Those 5 officials are also party members, because all delegates are party members.

This reasoning works for all ‘some’ statements. If a sufficient condition is part of a some statement, you can replace it with the necessary condition.

Here’s a diagram that shows both conclusions we can make from the facts in the argument. Notice that I am replacing the sufficient condition in the some statement with the necessary condition:

D ➞ PM    +    D Some GO    =         PM Some GO

GO ➞ S     +    GO Some D     =        S Some D

I think you’re better off working towards an intuitive understanding of ‘some’ statements.

• Some statements are reversible.
• You can make a deduction when part of a some statement is also a sufficient condition
• You cannot make a deduction when part of a some statement is also a necessary condition

So “Cat ➞ Tail, Cats Some Black” lets you conclude “some things with a tail are black”

“Cat ➞ Tail, Tails Some monkeys” does not let you conclude that some cats are monkeys.

___________

1. This gets the first fact backwards.
2. This is possible, but it doesn’t have to be true.
3. CORRECT. Some delegates are government officials, and all officials are speakers.
4. This gets the third fact backwards.
5. We only know that some government officials are party members.