June 2010 LSAT Section 5 Question 18

Based on the passage, it can be concluded that the author and Broyles-González hold essentially the same attitude toward

Anna20 on May 7, 2020

Sufficient in Common

Apologies in case this has been previously covered (there's quite a few comments on this thread and I haven't seen this). Rule 2 for making a valid deduction is that they must have the Sufficient in common. In example 3, we set out A-some-B and B --> C. It is then explained that the sufficient in this example is "in common". However, the first exercise on the next page is W-some-U and W --> V, where it is also noted that the sufficient is "in common". What am I missing - how can the sufficient be in common for each of these?

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Anna20 on May 29, 2020

Please can I follow up on this. Thank you.

Skylar on May 29, 2020

@Anna2020, happy to help!

The term "sufficient condition" is referring only to the variable's role in the S->N statement, not in the quantifier statement.

In the first example you mentioned, we have the S->N statement "B->C." Here, B is the sufficient condition and C is the necessary condition. The some statement "A-some-B" also has the variable B, which we identified as the sufficient condition, so we can say they have the sufficient condition in common and connect the two statements with the arrow pointing away from the quantifier.

In the second example you mentioned, we have the S->N statement "W->V," where W is the sufficient condition and V is the necessary condition. The some statement "W-some-U" has W, which we identified as the sufficient condition, so we can say they have the sufficient condition in common and connect the two statements with the arrow pointing away from the quantifier.

Does that make sense? Please let us know if you have any other questions!