LSAT Explanation PT 29, S1, Q15: Ordinary mountain sickness, a common condition

LSAT Question Stem

Which one of the following is an assumption on which the argument depends? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

Let's first break down the argument in the passage. The argument states that ordinary mountain sickness and cerebral edema are both caused by a shortage of oxygen at high altitudes. Cerebral edema is a more dangerous condition than ordinary mountain sickness because it can quickly become life-threatening if not treated correctly from its onset. The argument concludes that cerebral edema is especially dangerous at high altitudes because its symptoms resemble those of ordinary mountain sickness, which may cause people to misdiagnose and mistreat the condition.

To better understand the argument, let's use a simple parallel example. Imagine two types of headaches - one is a common, harmless headache, and the other is a rare, dangerous headache that can become life-threatening if not treated properly. If both types of headaches have similar symptoms, it would be difficult to identify the dangerous headache, making it especially dangerous because people might not treat it correctly.

Now, let's move on to the question. This is a Necessary Assumption question, which means we need to identify an assumption that the argument depends on for its conclusion to be valid.

Let's discuss each answer choice:

a) The treatment for ordinary mountain sickness differs from the treatment for cerebral edema.

If the treatments were the same, then even if someone misdiagnosed cerebral edema as ordinary mountain sickness, they would still receive the correct treatment, and the danger would be mitigated. If this statement were false, the conclusion would be weakened. Therefore, this is a necessary assumption for the argument.

b) Cerebral edema can cause those who suffer from it to slip into a coma within a few hours.

This answer choice, while providing additional information about the dangers of cerebral edema, is not a necessary assumption for the argument. The argument's conclusion would still hold even if this statement were false.

c) Unlike cerebral edema, ordinary mountain sickness involves no disruption of blood circulation in the brain.

This statement provides a distinction between the two conditions but is not necessary for the argument. The conclusion focuses on the danger posed by the similarity of symptoms, not the differences in the conditions.

d) Shortage of oxygen at extremely high altitudes is likely to affect thinking processes and cause errors of judgment.

This answer choice introduces a new idea about the effects of oxygen shortage on thinking processes. However, it is not necessary for the argument, as the conclusion is based on the similarity of symptoms, not the potential for errors in judgment.

e) Most people who suffer from ordinary mountain sickness recover without any special treatment.

While this statement provides information about the recovery from ordinary mountain sickness, it is not a necessary assumption for the argument. The conclusion would still hold even if this statement were false.

In conclusion, the correct answer is A, as it is a necessary assumption for the argument. The argument depends on the assumption that the treatments for ordinary mountain sickness and cerebral edema are different, making it more dangerous for cerebral edema to be misdiagnosed as ordinary mountain sickness at high altitudes.