LSAT Kung Fu Forum / Substitution Rule Question

Substitution Rule Question

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Feb 20 2014

kaveh180

Substitution Rule Question

I just watched the video for Practice Test 61, Section IV, Game #2, which happens to be our first substitution question covered (to my knowledge). I watched the video carefully, and I just want to ask to make sure: in step 2 of our system, is it imperative to ignore the rule in question from the original rules when attempting to prove the new rule wrong? For example, question 11 asks to substitute the rule that the necklace and jar are both older than the tureen. However, I didn't notice you specifically approach the problem in a way that voids that rule (or at least I didn't hear you explicitly declare that).

So basically, is it correct when performing step 2 of our substitution question system to graph the new rule we are testing while following all the old rules, except the rule that we are supposed to be substituting?

Sorry this is a little confusing to ask through the forum. I hope this is understandable.

Thanks again,
Cameron

Feb 21 2014

majorgeneraldave

These questions are the most complex questions asked. They demand two actions: The correct answer must create all of the same conditions as the rule it replaces, and it must create only those conditions.

This gives us a 2-part approach:

1. Disprove the bad answers. Use your prior work to disprove bad answer choices. The correct answer should have only the same effects as the rule it replaces, so you can eliminate any answer choice that isn't proven true in every line of your prior work. This step is exactly the same as our method for dealing with Must Be True questions.

2. Disprove the Old Rule. Using the remaining two or three answer choices, plug them into your diagram and attempt to disprove the old rule. A correct substitution would be the same as the old rule in all instances, so if you can make an answer choice true and at the same time invalidate the old rule, that means that answer choice isn't the same as the rule it's meant to replace. Get rid of it.

Clear?

Apr 15 2014

(Reply to #2) #3

kaveh180

Yes, I got it; thank you. Amazing how helpful bold and italics can be sometimes. And plus, after working through a couple more the approach became very clear.

To simplify this approach further, I like to think of it as step one: False-True; and step two: True-False. That is, for step one, see where the substitute rule is false in the prior answer choices and the original rule is true (since it's from prior work). Then, for step two, make the substitute rule True and see if that makes the original rule false. False-True. True-False.

Helps for me, at least!

Apr 15 2014

(Reply to #3) #4

majorgeneraldave

I like it!

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