LSAT Explanation PT 42, S4, Q26: Essayist: Common sense, which is always

LSAT Question Stem

If all of the essayist's statements are true, then which one of the following must be true? 

Logical Reasoning Question Type

This is a Must Be True question. 

Correct Answer

The correct answer to this question is E. 

LSAT Question Complete Explanation

Let's first analyze the passage. The essayist claims that common sense is a collection of theories that have been tested over time and found useful. As new, more useful theories are developed, they gradually replace the older theories in common sense, causing it to progress. However, because common sense absorbs new theories slowly, it always contains some obsolete theories.

Now, let's identify the question type and what it's asking us to do. This is a Must Be True (MBT) question, meaning we need to find the answer choice that must be true based on the information provided in the passage.

Let's examine each answer choice in detail:

a) This answer choice claims that some new theories that have not yet been found more useful than any current common sense theory will never be absorbed into the body of common sense. However, the passage does not provide any information about the future usefulness of these new theories, so we cannot prove that this must be true.

b) This answer choice compares the usefulness of older and newer theories within the body of common sense. The passage, however, does not make this comparison. It only compares the usefulness of theories within common sense to those not yet part of common sense. Therefore, we cannot prove that this must be true.

c) This answer choice suggests that the frequency of new theories being generated prevents their rapid absorption into common sense. The passage does not provide any information about the frequency of new theories or the reason for their slow absorption. Thus, we cannot prove that this must be true.

d) This answer choice states that each theory within the body of common sense is eventually replaced with a new, more useful theory. Although the passage mentions that some theories are replaced by more useful alternatives, it does not guarantee that every single theory will be replaced. Therefore, we cannot prove that this must be true.

e) This answer choice claims that at least some useful theories that have been tested over time are less useful than some other theories not yet fully absorbed into common sense. Since the passage states that common sense always contains obsolete theories and is always progressing, we can infer that there must be some more useful theories outside of common sense that have not yet replaced the obsolete ones. Thus, this answer choice must be true based on the information provided.

The correct answer is E.