LSAT Explanation PT 20, S4, Q18: Dobson: Some historians claim that the

LSAT Question Stem

Which one of the following is an error of reasoning in Dobson's argument? 

Logical Reasoning Question Type

This is a Flaw question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage. Dobson's argument is structured as follows:

Premise: Some historians claim that the people who built a ring of stones thousands of years ago in Britain were knowledgeable about celestial events because two of the stones determine a line pointing directly to the position of the sun at sunrise at the spring equinox.

Premise: There are many stones in the ring, so the chance that one pair will point in a celestially significant direction is large.

Conclusion: Therefore, the people who built the ring were not knowledgeable about celestial events.

An "Evaluate" question for this argument could be: "Is the alignment of the stones with the sun at the spring equinox a mere coincidence or an intentional design?"

Now, let's discuss the question type and the answer choices. This is a Flaw question, which asks us to identify an error of reasoning in Dobson's argument.

a) The failure of cited evidence to establish a statement is taken as evidence that that statement is false.

This is the correct answer. Dobson's argument assumes that because the probability of one pair of stones pointing in a celestially significant direction is large, the historians' claim must be false. However, just because the cited evidence doesn't definitively prove the historians' claim, that doesn't mean their claim is false.

b) Dobson's conclusion logically contradicts some of the evidence presented in support of it.

This answer choice is incorrect because there is no logical contradiction between Dobson's conclusion and the evidence he presents.

c) Statements that absolutely establish Dobson's conclusion are treated as if they merely give some support to that conclusion.

This answer choice is incorrect because there are no statements in the argument that absolutely establish Dobson's conclusion.

d) Something that is merely a matter of opinion is treated as if it were subject to verification as a matter of fact.

This answer choice is incorrect because Dobson's argument does not treat any opinions as if they were factual claims. His argument is based on the probability of the stones' alignment, not on opinions.

e) Dobson's drawing the conclusion relies on interpreting a key term in two different ways.

This answer choice is incorrect because there is no equivocation of meaning in Dobson's argument.

In summary, the correct answer is A, as Dobson's argument commits the error of reasoning that the failure of cited evidence to establish a statement is taken as evidence that that statement is false.