Difficult Trait #7&8

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LR Perfection Free Preview: Chapter 3 Part VII

Difficult Trait #7: Placing the intermediate conclusion at the end of the stimulus, and prefacing it with words like “thus,” “therefore,” or “as a result.”

Be extra careful here. If you see a statement at the very end of a stimulus/argument, beginning with words like “thus” or “therefore,” it doesn’t automatically mean that it’s a trap intermediate conclusion posing as the main conclusion!

In easier questions, it may very well be the argument’s main conclusion. But because the test makers know that we are so used to having the main conclusion as the very last sentence, they will sometimes put the intermediate conclusion last on purpose. Let’s go back to our EV example from earlier:

The price of gasoline is going through the roof, more and more people are buying electric vehicles in order to save money. Thus, the internal combustion engine is doomed.

Nothing out of the ordinary here. The first statement is the premise, the second is the intermediate conclusion, and the last sentence is the main conclusion.

But what if we switched it up a little bit?

The internal combustion engine is doomed. The price of gasoline is going through the roof. As a result, in order to save money, more and more people are buying electric vehicles.

We have the exact same argument, but the intermediate conclusion is placed last this time. If we weren’t careful, we might have easily mixed up the intermediate and main conclusions.

So the story’s moral is to think about the support relationship between each statement within the argument.

Based on indicator words and location in the stimulus alone, there’s just no way to determine which statement is the intermediate conclusion and which statement is the main conclusion.

PT43 S3 Q23

Each of many different human hormones can by itself raise the concentration of glucose in the blood. The reason for this is probably a metabolic quirk of the brain. To see this, consider that although most human cells can produce energy from fats and proteins, brain cells can use only glucose. Thus, if blood glucose levels fall too low, brain cells will rapidly starve, leading to unconsciousness and death.

Which one of the following most accurately expresses the main conclusion of the argument above?

A. Each of many different human hormones can by itself raise blood glucose levels

B. The reason that many different hormones can each independently raise blood glucose levels is probably a metabolic quirk of the brain

C. Although most human cells can produce energy from fats and proteins, brain cells can produce energy only from glucose

D. If blood glucose levels fall too low, then brain cells starve, resulting in loss of consciousness and death

E. The reason brain cells starve if deprived of glucose is that they can produce energy only from glucose

 

The reason we have included this question is to do a deeper dive into the importance of having a clear understanding of a stimulus’ structure, to differentiate between what portion of the stimulus forms the argument and what forms the peripheral information. We also do this to further differentiate between premises, the intermediate conclusion, and the main conclusion.

Before we move to the actual question, I just wanted to clarify a persistent point of confusion many students face when discussing a stimulus’ structure. Remember that most LR stimuli will contain an argument (premise, conclusion, and maybe an intermediate conclusion), and the LSAT will often use logic (most frequently conditional logic and causation logic, we will look at this soon) to advance the argument, to get from premise to conclusion.

But in an argument that uses causal logic, cause – effect does not mean premise and conclusion. Let’s look at two different examples:

Smoking is a leading cause of lung cancer, John smokes two packs a day, therefore he will surely get lung cancer.

What is the causal relationship here? Smoking ⇒ Cancer. John smokes; therefore, he will get cancer. The conclusion is that John will get cancer. Simple enough, right?

Now take a look at the next example:

Smoking is a leading cause of lung cancer, John has lung cancer, therefore he must surely have been a heavy smoker.

The causal relationship here is still the same, Smoking ⇒ Cancer. But the premise is that John has lung cancer (effect), while the conclusion points to the cause for this effect (John is a smoker). So here, the logical relationship between cause and effect is essentially reversed in the argument’s structural pattern. The effect is identified and the cause is actually the conclusion.

The stimulus describes a phenomenon (different hormones can raise glucose concentration), and then proceeds to offer up an explanation for it. In other words, metabolic quirk of the brain is the cause, and hormones raising glucose concentrations is the effect in this causal relationship. But that doesn’t mean the effect is the conclusion of the argument!

The author then goes on to talk about why glucose is so important to the brain (brain cells can use only glucose…if glucose levels fall too low, brain cells will starve).

So the argument presents three different elements:

  1. Different hormones can raise glucose levels
  2. This is due to the brain
  3. Glucose is really important to the brain

When simplified, it is not hard to see that the first statement is a fact/background information, the second statement is the author’s opinion, and the last statement is the support that the author provides for the second statement.

So from a causational logic perspective, metabolic quirk of the brain ⇒ different human hormones being able to raise glucose levels by themselves;

But from a structural perspective, glucose being important to the brain (third and fourth sentence of the stimulus) are the premise and intermediate conclusion, respectively; the second sentence, “the reason for this is probably a metabolic quirk of the brain,” is the conclusion.

A. Each of the many different human hormones can by itself raise blood glucose levels

This is the most commonly selected wrong answer: it’s the phenomenon that the author is seeking an explanation for. Yes, it’s the effect in the cause – effect relationship, but it is not the conclusion. If you had selected this as the answer, you would have fallen into the trap of not distinguishing between an argument’s logical and structural pattern.

B. The reason that many different hormones can each independently raise blood glucose levels is probably a metabolic quirk of the brain

This is the correct answer.

C. Although most human cells can produce energy from fats and proteins, brain cells can produce energy only from glucose

This is the support/premise provided by the author for why it’s the brain that is responsible for allowing different hormones to independently raise glucose levels.

D. If blood glucose levels fall too low, then brain cells starve, resulting in loss of consciousness and death

This is the intermediate conclusion of the argument. Structurally, as we mentioned previously, the argument goes like this:

Brain cells can only use glucose (premise) → Low glucose is fatal (intermediate conclusion) → Brain makes sure hormones can produce glucose (conclusion)

Frequently, as per Trait #7, the test makers will put the intermediate conclusion at the end of the stimulus and preface it with words like “thus,” “as a result,” or “therefore.” They are trying to trick us into thinking it’s the main conclusion when it’s not. Remember, other elements of the argument will always support the actual main conclusion, whereas the intermediate conclusion, while supported, will go on to support another idea.

E. The reason brain cells starve if deprived of glucose is that they can produce energy only from glucose

This is a summary of the premise and intermediate conclusion of the argument.

In LR questions, the test makers will often present a result/situation, then provide an explanation or cause for it. In such instances, the conclusion is the explanation for the phenomenon described and thus the causation part of the cause – effect relationship. This brings us to the final recurring trick employed in Find the Conclusion Questions:

Difficult Trait #8: When there is a cause/effect relationship in the argument, sometimes the effect is the premise and the cause is the conclusion. Don’t always assume that because cause ⇒ effect, cause = premise, and effect = conclusion.

Whenever we see a causal relationship in the stimulus, many students will erroneously assume that the cause is the premise and the effect is the conclusion.

Don’t make this mistake!

In a causation-based argument, the cause – effect relationship and the premise – conclusion relationship are two discrete elements that we must analyze independently.