LSAT Explanation PT 27, S1, Q16: Recent research shows that sound change

LSAT Question Stem

Which one of the following, if assumed, does most to justify the argument's conclusion? 

Logical Reasoning Question Type

This is a Strengthen question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage. The passage states that recent research shows that sound change in a language is not gradual, but rather, new sounds often emerge suddenly. This contradicts the classical account of sound change, which is based on gradualness. As a result, the author concludes that since the classical account must be discarded, sound-change theory in general must also be discarded. Here's the structure of the argument:

Premise: Sound change is not gradual.

Premise: The classical account of sound change is based on gradualness.

Conclusion: Sound-change theory in general must be discarded.

Now, let's think of an "Evaluate" question for this argument: "Do all theories of sound change rely on the classical account?"

The question type of this problem is Strengthen, which means we're looking for the answer choice that, if assumed, does the most to justify the argument's conclusion.

Let's go through the answer choices:

a) The data on which the classical account of sound-change theory was based are now known to be inaccurate.

- This answer choice doesn't strengthen the argument, because we already know from the passage that the classical account's central tenet of gradualness is wrong. Adding information about the inaccuracy of the data doesn't help us conclude that sound-change theory in general must be discarded.

b) The emergence of new sounds appears to be random.

- This answer choice is irrelevant to the argument. Whether the emergence of new sounds is random or not doesn't help us justify the conclusion that sound-change theory in general must be discarded.

c) The meeting of linguistically disparate cultures can affect the sounds of their languages in unpredictable ways.

- This answer choice is also irrelevant to the argument. The reason why sound changes (such as culture clashes) doesn't matter. What matters is whether the sound-change theory works or not.

d) All theories of sound change rely heavily on the classical theory.

- This is the correct answer choice. If all theories of sound change rely on the classical theory, then the fact that the classical theory is wrong means that sound change theory in general must also be wrong. This assumption strengthens the argument and helps justify the conclusion.

e) For most languages, historical records of their earlier stages are scarce or nonexistent.

- This answer choice is out of scope. The availability of historical records doesn't help us justify the conclusion that sound-change theory in general must be discarded.

In conclusion, the correct answer is D, as it strengthens the argument by showing that if all sound change theories rely on the classical theory, then discarding the classical theory means discarding sound-change theory in general.