Whenever Joe's car is vacuumed, the employees of K & L Auto vacuum it; they are the only people who ever vacuum J...

Sangwook on January 13, 2014

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On the choice (a), it says "...since the only time she drinks water in the morning is when she takes her medication." According to your lectures, "the only" is a sufficient condition. On the other hand, "when" is also a sufficient condition, right? Then, in this sentence which one should I apply it to the sufficient condition? If it is "the only", then could you please why "when" in this sentence is not a sufficient condition? Thanks,

3 Replies

Melody on January 18, 2014

The words "the only" will always introduce a sufficient condition. "When" can also introduce a sufficient condition. You must first ask yourself, what is a sufficient condition? A sufficient condition is the condition that proves the existence of the necessary condition. It is what is dependent on the necessary condition, while the necessary condition is independent of the sufficient condition.

So looking at the sentence: "the only time she drinks water in the morning is when she takes her medication," we must decide what is dependent on what. Is her taking medication dependent on her drinking water, or is her drinking water dependent on her taking medication? We see with the wording in this statement that Emily drinking water is dependent on her taking medication: THE ONLY TIME (so at no other time) she drinks water in the morning is when she takes medication. That means she can still take medication without drinking water, but, she can never drink water without taking medication. As a rule, "the only" will always be followed by the sufficient condition. With the word "when," you must be careful to analyze the sentence as we just did and truly decipher which condition is dependent on the other.

Hope that was helpful! Let us know if you have any other questions!

Sangwook on January 19, 2014

Superb!!! Two thumbs up!!!! ^^
Thanks a lot,

Richard on July 10, 2016

I initially got this question wrong but only because I rushed through it thinking that I could answer it correctly without diagramming the formal logic. When I went back to it, paused the timer and diagrammed the formal local in the stem and answer choices, it was a lot easier. This really begs the question however, what is the determining factor for deciding when to diagram formal logic on a LR question versus simply thinking about the answer in your head?

It seems that diagramming formal logic on a given LR question has clear benefits with respect to accuracy, however the obvious drawback is the amount of time it takes. This is especially true if you are diagramming formal logic for each answer choice. A good example of where this would come into play is on a parallel reasoning question, such as this one. What are your suggestions in regards to timing with this particular issue in mind?