So I'm two months into studying for the Oct. LSAT and am working on improving my accuracy regarding necessary assumption questions. I encountered 2 problems from practice tests (PT 56 Section 3 # 18 "Fund-raiser" and PT 3 Section 2
#3 "In Europe school children devote") that require you to find a nec. assumption.
For
#3 from PT 3 section 2, I was between answer choice A and the correct answer, D. I chose D because it would destroy the argument if negated, but I couldn't eliminate A (All children can be made physically fit by daily calisthenics). I looked on LSAT forums online and one reason cited as to why the A was incorrect was that the answer choice makes daily calisthenics sufficient and not necessary (which contradicts the conclusion that states that calisthenics is necessary for physical fitness).
However, I diagrammed answer choice A as All children can be made physically fit---> by daily calisthenics
According to the forums online and speaking to other students, my diagram above is wrong. My question is why is it wrong and how would I diagram this answer choice. Does "by" indicate the sufficient condition and I'm just unaware of this or is there another method as to how we can diagram conditionals without indicator words like (if or without)?
Comments
A can be diagrammed as "C-->MPFBC", that is "if you are a child, then you can be made physically fit by daily calisthenics." This does have an indicator: the word "all." All introduces the sufficient condition; for example, "All apples are fruits" can be diagrammed as A-->F. Or, "All dogs have spots" is: "D-->HS".
The reason why A is incorrect is that the author is not assuming anything about ALL children; the conclusion is only about North American children, so it does not have to be true that all children can be made physically fit only if they participate in calisthenics programs.
I see that for the last question "all" is an indicator but for this question there doesn't seem to be any
Answer choice E does this for us. If the emotional connection donors feel to a charity (which can be gained through voting) does not affect the amount of money they are willing to give, then the conclusion falls apart.
On the diagramming side:
Charities --most--> Probably can increase the amount of money they raise by giving donors the right to vote.
But as you can see, this isn't really helpful; it's just diagramming for diagramming's sake.
Upon review I realized that this diagram did not get me to the correct answer (which was the gap if successful then it must be bought by prime purchasers; however, the reverse of the diagram above, teach ppl software that demands---> expensive, got me to this gap..
How would you gauge that expensive is the nec? Is it because you can reason that if it demands the memorization of unfamiliar commands it must be expensive
1st Sentence: ET-->/PPBS
If introduces the sufficient condition here (I rephrased costs of training staff to use it as expensive to teach to keep the variables consistent throughout the premises; this is actually key for us to build our conditional chain, and it rests on the realization that "costs of training staff to use software are high" is essentially the same as "expensive to teach people a software"; costs are high=expensive; training=teaching)
2nd: DMU--> ET
"We know that it is expensive to teach people a software that demands memorization of unfamiliar commands" means: if a software DMU commands, then it is ET.
3rd (conclusion sentence): S--> /DMU
"To be successful, a software cannot require DMU" means: if a software is successful, it must be true that it does not DMU commands.
So we have to use 1 and 2, along with a sufficient assumption, to prove 3:
DMU-->ET-->/PPBS
Conclusion: DMU-->/S (the contra positive of the 3rd sentence)
Because our sufficient variables line up, we just need to add a /S to the end of our conditional chain to transitively prove the conclusion:
DMU-->ET-->/PPBS-->/S
The new relationship above, /PPBS-->/S, is out sufficient assumption! It allows us to prove the conclusion.
Luckily, C is the contrapositive of this new premise, so we know that we did our work correctly. C reads: S-->PPBS, if a software is successful, then prime purchasers will buy it.
Your reply is so helpful. A follow up question, shall we diagram question when there is no clear logic indicator? Also, when the premises says that B is causes by A, could we write as A-->B? Is conditional logic and causation the same thing? Thank you so much.