Necessary/ Sufficient in Linear Setups

[Mark Yerrid]

Hello.

I am having issue with certain 'rules' in the linear setups. I am not sure if I will find these in other games; however, if so, I can be prepared now by getting this cleared up. If you look at page 3-21 (Game 4 Dec.1997), the next-to-last last rule states:

Lalitha performs third ONLY IF Norton performs fifth. .

I know that Norton is the Necessary condition based on the "only if" statement, but does this mean that "N" (Norton) can perform fifth as much as he wants (or whenever he wants) BUT that Lalitha does/does not HAVE TO perform third? In other words, "N" can perform 5th, but this DOES NOT MEAN that "L" is going to perform 3rd. I believe it means that if L performs 3rd-----N has to be in the 5th spot.


I have all three Bibles as well as the homework books (1-12). I had taken the virtual course in the past, but did not complete it. Is there somewhere I can look to improve on this types of "rules"? I know I have read this in the past, however;cannot recall the section. I know that I am confusing one condition for another; I know that a condition (S or N) can be in one place but this DOES NOT denote the other "has to be" there such as the example above.

Thank you.
Mark

[Dave Killoran]

Hi Mark,

Thanks for the message. Let me try to address a few points from your post.

First, you will definitely see a lot of conditional rules in Logic Games. Grouping games, in particular, feature numerous conditional rules, but they show up frequently in other game types as well.

Second, your understanding of the L3 N5 relationship is correct. Once N is fifth, L can be third, but L does not have to be third (to make the false assumption that N being fifth forces L to be third is what we call a Mistaken Reversal.). However, if L is third, then N must be fifth.

Further, if L is not third, then N can be fifth but N does not have to be fifth (once the sufficient condition is not met, anything can happen).

If N is not fifth, then this enacts the contrapositive and L cannot be third. Thus, we have covered what occurs when each condition both occurs and does not occur; as you can see, in some instances, not everything is perfectly determined.

Finally, the Virtual course has some great info on conditional reasoning (and some great modules), but the easy way for you to get up to speed on these rules is to go to the LSAT Logical Reasoning Bible you have, and read Chapter Six (and later Chapter 13 as that will really solidify your understanding). After you get through Chapter Six, move back to the Virtual Course material and check out the conditional modules there as that will expand on those concepts and refine your understanding.

Good luck and feel free to post back any questions you have!

[Mark Yerrid]

Dave,

Thank you very much for answering this question. Ironically, I opened my Logic Games Bible last night, and on page 30..the very same question I asked you was defined. I do appreciate the extra reading you suggested: Chapter 6 and Chapter 13 which I will now delve into. Your explaination was very easy to understand (via email). Thank you again for going into so much detail. It 'clicked' for me after reading your process.

Sincerely,
Mark