October 2010 LSAT Section 1 Question 27

As it is presented in the passage, the approach to history taken by mainstream U.S. historians of the late nineteenth...

MeganJ27 on February 2, 2020

Question 4

In question 4 I'm not understanding how moss and jones is a possibility for day 4 The rules says that if jones views on day one, then hall views on day 2. The question began with hall on day 2 so doesn't that automatically mean jones is on day 1?

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SamA on February 4, 2020

Hello @MeganJ27,

This is a very important lesson for you. Remember that the necessary condition does not guarantee the sufficient condition. You will be tested on this concept frequently, in both logic games and logical reasoning.

I'll explain.

Our rule says: If Jones views the site on day 1, Hall views the site on day 2.

J1 - - - - - - - - - - > H2
suf nec

We are given that Hall is on day 2, which is our necessary condition. However, this does not mean that Jones will be on day 1. The necessary condition can exist without the sufficient condition.

By placing H on day 2, we can only say that J could be on day 1. J is free to go wherever, limited only by the other rules.

If this question had given us J1, then we could have placed H2. But it does not work the other way around. Necessary does not guarantee sufficient.

It can take a while to be comfortable with conditional reasoning, but it is worth it. If you can get a good understanding of sufficient and necessary conditions, your score will improve dramatically.

MeganJ27 on February 6, 2020

Thank you! I'm still memorizing everything, your explanation was extremely thorough. Thank you!