LSAT - Law School Admission Necessary and Sufficient Assumptions Questions and Answers

Question 1

Nutritionist: Any beverage that contains a high amount of refined sugar is unhealthy. Since many popular fruit juices are high in naturally occurring sugars and not refined sugar, they are, contrary to popular belief, actually healthy.

Accepted Answer

Beverages that are high in naturally occurring sugars are not unhealthy.

Answer

The nutritionist's argument has a gap. The premise is about 'refined sugar' making drinks unhealthy. The conclusion is about drinks with 'naturally occurring sugars' being healthy. The argument assumes that because these juices lack the unhealthy component (refined sugar), they must be healthy. This requires assuming that the other type of sugar present (naturally occurring) does not also make them unhealthy. Answer choice B fills this gap perfectly. If beverages high in naturally occurring sugars are not unhealthy, the conclusion that these specific fruit juices are healthy is properly supported.

Question 2

Political Analyst: A candidate who does not win the support of young voters will not be elected president. Since candidate Miller has focused her campaign on issues that are of primary concern to young voters, she is likely to be elected president.

Accepted Answer

Focusing a campaign on issues of primary concern to young voters is sufficient to win their support.

Answer

This is a sufficient assumption question. The argument's structure is: Premise 1: Not winning young voters -> Not elected. Premise 2: Miller focused on young voters' issues. Conclusion: Miller will be elected. There's a leap from 'focusing on their issues' to 'winning their support' and another from there to being 'elected'. The correct answer must bridge this gap completely. Answer A, if assumed true, connects the premise (focusing on issues) to the necessary condition for winning (winning their support), making the argument logically valid. Specifically, it guarantees Miller wins the support of young voters, which allows the conclusion to be drawn.

Question 3

Historian: To be considered a truly great military leader, one must have demonstrated strategic brilliance on the battlefield. Alexander the Great is widely considered a truly great military leader.

Accepted Answer

Alexander the Great demonstrated strategic brilliance on the battlefield.

Answer

This is a necessary assumption question. The argument presents a rule (Great Leader -> Strategic Brilliance) and then states an example that fits the 'Great Leader' category. For the example to be consistent with the rule, the example must also possess the quality mentioned in the rule. The argument requires the unstated premise that Alexander the Great actually meets the condition set forth for all great military leaders. If Alexander did NOT demonstrate strategic brilliance, the argument would fall apart. Therefore, assuming he did is necessary. The Negation Test works here: if Alexander the Great did *not* demonstrate strategic brilliance, the premise and conclusion would be contradictory.

Question 4

An assumption that, if true, is by itself enough to guarantee the truth of the argument's conclusion is known as what?

Accepted Answer

A sufficient assumption

Answer

This question tests the definition of a sufficient assumption. A sufficient assumption is a premise that, when added to an argument's existing premises, makes the conclusion logically certain. In other words, if the sufficient assumption is true, the conclusion *must* be true. A necessary assumption, by contrast, is something that must be true for the conclusion to even be possible, but it doesn't guarantee the conclusion on its own.

Question 5

Ecologist: The population of monarch butterflies has declined sharply in recent years. This decline is due to the widespread use of herbicides that destroy milkweed, which is the sole food source for monarch caterpillars. Therefore, to increase the monarch butterfly population, we must restrict the use of these herbicides.

Accepted Answer

Restricting the use of the herbicides will lead to an increase in the amount of available milkweed.

Answer

The argument identifies a cause (herbicide destroys milkweed) for a problem (butterfly decline) and proposes a solution (restrict herbicides) to achieve a result (increase butterfly population). The argument assumes that the proposed action will actually reverse the causal chain. It assumes that restricting herbicides will lead to more milkweed. Without this link, the conclusion that the butterfly population will increase does not follow from the premise. This is a necessary assumption. If restricting herbicides did *not* lead to more milkweed, the proposed solution would be ineffective.

LSAT - Law School Admission Test Practice Test

LSAT - Law School Admission Test Practice Test

LSAT - Law School Admission Necessary and Sufficient Assumptions Questions and Answers