LSAT - Law School Admission Necessary and Sufficient Assumptions Questions and Answers — 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.
- Some beverages that are high in naturally occurring sugars are also high in refined sugar.
- Beverages that are high in naturally occurring sugars are not unhealthy. (Correct answer)
- The most popular fruit juices are the ones with the most naturally occurring sugar.
- Refined sugar is more harmful to the body than naturally occurring sugar.
Correct answer: Beverages that are high in naturally occurring sugars are not unhealthy.
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.
- Focusing a campaign on issues of primary concern to young voters is sufficient to win their support. (Correct answer)
- No other candidate has focused on issues of primary concern to young voters.
- Issues of primary concern to young voters are the most important issues in the presidential election.
- Candidate Miller will win the support of young voters.
Correct answer: Focusing a campaign on issues of primary concern to young voters is sufficient to win their support.
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.
- All leaders considered truly great have demonstrated strategic brilliance.
- Only military leaders can be considered truly great.
- Alexander the Great demonstrated strategic brilliance on the battlefield. (Correct answer)
- Strategic brilliance is the only quality required to be a great military leader.
Correct answer: Alexander the Great demonstrated strategic brilliance on the battlefield.
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?
- A counter-premise
- A necessary assumption
- A sufficient assumption (Correct answer)
- An auxiliary conclusion
Correct answer: A sufficient assumption
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.
- The use of herbicides is the only factor negatively affecting the monarch butterfly population.
- Restricting the use of the herbicides will lead to an increase in the amount of available milkweed. (Correct answer)
- Monarch butterflies are an important part of the ecosystem.
- Farmers will comply with any new restrictions on herbicide use.
Correct answer: Restricting the use of the herbicides will lead to an increase in the amount of available milkweed.
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.
Question 6: Art Critic: Any painting created by a master of the Renaissance period is a masterpiece. The painting 'Sunrise over the Harbor' is not a masterpiece.
- Some paintings that are not masterpieces were created by masters of the Renaissance period.
- No master of the Renaissance period created the painting 'Sunrise over the Harbor'.
- 'Sunrise over the Harbor' was painted by an artist who was not a master of the Renaissance period. (Correct answer)
- Only paintings created by masters of the Renaissance period can be masterpieces.
Correct answer: 'Sunrise over the Harbor' was painted by an artist who was not a master of the Renaissance period.
This argument relies on a conditional statement: If created by a Renaissance Master (RM), then it is a Masterpiece (M). The second premise is that a specific painting is Not a Masterpiece (~M). The conclusion follows from the contrapositive of the first statement. The contrapositive is: If Not a Masterpiece (~M), then Not created by a Renaissance Master (~RM). The argument assumes this logical step. Answer C states the conclusion of this contrapositive (~RM), which is a necessary assumption for the argument to be valid. In fact, in this deductive context, it's also sufficient to make the argument logically complete.
LSAT - Law School Admission Necessary and Sufficient Assumptions Questions and Answers
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.