Identify
Assumptions
Master the art of finding hidden premises that hold arguments together: the single most tested critical reasoning skill on the GRE.
What Is an Assumption?
An assumption is an unstated belief that must be true for the argument's conclusion to follow from its premises. It is the invisible bridge between evidence and conclusion: without it, the argument collapses.
Anatomy of an Argument
Why This Matters on the GRE
The Core Rule of Assumptions
This gives us a powerful test: the Negation Test. Negate a potential assumption. If the argument falls apart, you have found a genuine assumption.
The Negation Test in Detail
Necessary vs Sufficient Assumptions
| Necessary Assumption | Sufficient Assumption | |
|---|---|---|
| Definition | Must be true; without it, the argument fails | If true, it guarantees the conclusion |
| Strength | Often modest and narrow | Often very strong and broad |
| Test | Negation Test: negate it, argument breaks | If you add it, the argument becomes airtight |
| GRE Frequency | Very common | Less common |
Common Assumption Gaps
How to Apply This on Test Day
Worked Example 1: Term Shift
Premise: More recyclable material is being collected.
Conclusion: Less waste will go to landfills.
Worked Example 2: Causal Leap
Premise: Breakfast eaters correlate with higher scores.
Conclusion: Breakfast causes higher scores.
Worked Example 3: Sampling Gap
Negation Test Applied
Let us negate the assumption from Example 3 and see what happens:
Common Mistakes
Assumption Cheat Sheet
| Gap Type | What to Look For | Assumption Pattern |
|---|---|---|
| Term Shift | New concept in conclusion | "X is related to Y" |
| Causal Leap | Correlation claimed as cause | "No alternative cause exists" |
| Sampling | Small group applied to all | "Sample is representative" |
| Analogy | Comparison between cases | "Cases are relevantly similar" |
| Implementation | Plan proposed with a goal | "No obstacle prevents success" |
Question 1 of 5
"Companies that offer flexible work schedules report higher employee satisfaction. Therefore, adopting flexible schedules will help Zenith Corp reduce its high employee turnover rate."
Which of the following is an assumption on which the argument depends?
Question 2 of 5
"A study found that people who drink green tea daily have a lower risk of heart disease. Researchers concluded that compounds in green tea protect the heart."
The researchers' conclusion relies on which of the following assumptions?
Question 3 of 5
"Since the city installed new LED streetlights on Elm Street, reported nighttime crimes on that street have dropped by 40%. The city council should therefore install LED streetlights throughout the city to reduce nighttime crime overall."
The argument assumes that:
Question 4 of 5
"Arcadia's public library saw a 30% increase in checkouts after it began offering e-books. The library director concluded that e-book availability is what drove the increase in total checkouts."
Which of the following, if true, would most undermine the director's conclusion?
Question 5 of 5
"In a survey of 500 Milltown residents, 70% said they would use a new community pool if one were built. The town board argues that building a pool would therefore be a sound investment because usage would be high."
The town board's argument depends on assuming which of the following?