LSAT Explanation PT 20, S4, Q21: Wirth: All efforts to identify a

LSAT Question Stem

The point at issue between Wirth and Chang is whether 

Logical Reasoning Question Type

This is a Disagree question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

To understand the disagreement between Wirth and Chang, let's first analyze the argument presented in the passage. Wirth's argument can be broken down as follows:

Premise 1: All efforts to identify a gene responsible for predisposing people to manic-depression have failed.

Premise 2: Nearly all researchers now agree that there is no "manic-depression gene."

Conclusion: If these researchers are right, any claim that some people are genetically predisposed to manic-depression is simply false.

Chang's counter-argument can be summarized as:

Premise: Many researchers have found evidence that a set of several genes is involved and that complex interactions among these genes produce a predisposition to manic-depression.

Conclusion: Wirth's conclusion is incorrect.

Now, let's consider the question type, which is a Point at Issue question. This means we're looking for the statement that best represents the disagreement between Wirth and Chang.

Answer Choices:

a) This answer choice is incorrect because both Wirth and Chang would agree that efforts to identify a single gene have failed. Chang, however, believes that a set of several genes is involved.

b) This answer choice is incorrect because neither Wirth nor Chang explicitly discuss the likelihood of researchers ever finding a single gene responsible for predisposing people to manic-depression.

c) This answer choice is incorrect because both Wirth and Chang agree that nearly all researchers now believe there is no single "manic-depression gene." Their disagreement lies in the possibility of multiple genes being involved.

d) This answer choice is correct because it represents the core disagreement between Wirth and Chang. Wirth believes that current research supports the claim that no one is genetically predisposed to manic-depression, while Chang argues that research indicates a set of several genes may be involved in predisposing people to the condition.

e) This answer choice is incorrect because it focuses on the thoroughness of the efforts made to find a gene, which is not the point of disagreement between Wirth and Chang. Their disagreement is about whether genetic predisposition to manic-depression exists or not.

In conclusion, the point at issue between Wirth and Chang is whether current research supports the claim that no one is genetically predisposed to manic-depression (answer choice d).