LSAT Explanation PT 45, S1, Q21: Although the geological record contains some

LSAT Question Stem

Which one of the following assumptions enables the argument's conclusion to be properly inferred? 

Logical Reasoning Question Type

This is a Sufficient Assumption question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

In this passage, the author discusses the relationship between major meteor impacts and mass extinctions. The argument structure is as follows:

Premise 1: Some hints of major meteor impacts precede mass extinctions in the geological record.

Premise 2: Many extinctions did not follow any known major meteor impacts.

Premise 3: Many records of major meteor impacts did not seem to be followed by mass extinctions.

Conclusion: The geological record suggests that there is no consistent causal link between major meteor impacts and mass extinctions.

The question type is a Sufficient Assumption question, which means we need to identify an assumption that, if true, would guarantee the conclusion to be properly inferred.

Before we discuss the answer choices, let's come up with an "Evaluate" question for this argument: "Is there any other evidence that could potentially establish a consistent causal link between major meteor impacts and mass extinctions?"

Now let's analyze the answer choices:

a) If there were a consistent causal link between major meteor impacts and mass extinctions, then all major meteor impacts would be followed by mass extinctions.

This answer choice is correct because it establishes a condition that would prove the conclusion. If it were true that a consistent causal link requires all major meteor impacts to be followed by mass extinctions, then the fact that there are many instances where this does not happen (as stated in Premise 3) would indeed suggest that there is no consistent causal link.

b) Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.

This answer choice is incorrect because it only strengthens the argument, but does not guarantee the conclusion. It states a necessary condition for a consistent causal link, but the fact that many mass extinctions followed major meteor impacts does not necessarily mean there is no consistent causal link.

c) Of the mass extinctions that did not follow any known major meteor impacts, few if any followed major meteor impacts of which the geological record contains no hints.

This answer choice does not bridge the gap to the conclusion about a consistent causal link. It only provides additional information about mass extinctions that did not follow any known major meteor impacts, which is not sufficient to prove the conclusion.

d) If there is no consistent causal link between major meteor impacts and mass extinctions, then not all mass extinctions could have followed major meteor impacts.

This answer choice relates the two terms we want connected, but the relationship is backwards. It is a mistaken reversal of the answer we need, where the sufficient condition should be the consistent causal link and the necessary condition should be the mass extinctions following major meteor impacts.

e) There could be a consistent causal link between major meteor impacts and mass extinctions even if not every major meteor impact has been followed by a mass extinction.

This answer choice actually undermines the conclusion, as it suggests that a consistent causal link could still exist despite the evidence provided in the passage.

In summary, the correct answer is A, as it establishes a condition that, if true, would guarantee the conclusion that there is no consistent causal link between major meteor impacts and mass extinctions.