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Necessary assumption LSAT questions ask what an argument depends on. Learn the negation test, see a worked example, and avoid answers that go too far.
Quick answer: a Necessary Assumption question asks what must be true for the argument to work. The best tool is the negation test: make the answer false. If the argument falls apart, that answer is the assumption.
The argument depends on assuming which one of the following?
Which one of the following is an assumption required by the argument?
The argument requires the assumption that…
How to Solve Necessary Assumption Questions
Find the conclusion and the evidence.
Find the gap between them.
Narrow it to two answers.
Negate each one by making it false.
Pick the answer whose negation breaks the argument.
Necessary Assumption Questions Example
This is a practice example we wrote to show the idea. It is not a real LSAT question.
Argument: The bakery will earn more next year, because it is adding a second oven that will double how much bread it can bake.
Question: The argument depends on which assumption?
Best answer: The bakery will be able to sell at least some of the extra bread.
Why: Negate it: “The bakery cannot sell any of the extra bread.” Now the second oven does not lead to more money, so the argument breaks. That is the test working.
Common Traps
Answers that would help but are not required.
Strong answers with words like “all” or “only.” The argument usually needs less than that.
Answers that are sufficient rather than necessary.
Necessary Assumption Questions FAQ
What is the negation test?
Make the answer false. If the argument then falls apart, the answer is a necessary assumption.
How do I negate a sentence?
Change it to the simplest opposite. “All” becomes “not all,” and “some” becomes “none.”
What is the difference between necessary and sufficient assumptions?
A necessary assumption must be true for the argument to work. A sufficient assumption would be enough to prove the conclusion.
