Lesson 13 of 46 · Reading Comprehension
Argument passages: conclusions, assumptions and flaws
Break a short argument into conclusion and evidence, find the unstated assumption that links them, and name the flaw when the link fails.
About 20 minutes
In this lesson
- Separate an argument’s conclusion from its evidence, using indicator words and the "why?" test.
- Find the assumption an argument depends on, and confirm it with the negation test.
- Recognise the common gaps between evidence and conclusion and describe them as flaws.
The idea
Arguments inside passages
Whether a passage is several paragraphs or a single short one, it often contains an argument: a claim supported by reasons. Some questions about it ask you to find the claim; others ask what the reasoning takes for granted, or where it goes wrong. These questions reward a different kind of reading from summarising: you are reading to find the weak joint.
Conclusion and evidence
The conclusion is the claim the author wants you to accept. The evidence (premises) is what is offered as the reason to accept it. Indicator words help:
| Before a conclusion | Before evidence |
|---|---|
| therefore, thus, so, hence, consequently, clearly, it follows that | because, since, for, given that, as shown by |
When there are no indicators, use the "why?" test. Take a candidate conclusion and ask "why should I believe that?" If the other sentences answer it, you have the conclusion. If the candidate itself answers "why?" for another sentence, it is evidence.
The conclusion is not always last. It can come first ("Clearly, the policy failed: …") or in the middle, and an argument can open with a view it is about to reject, as in "Some economists claim… Yet…". In that case the view reported first is not the conclusion; the author's answer to it is.
Assumptions: the missing link
An assumption is something the argument needs but does not state. It sits in the gap between the evidence and the conclusion. To find it, put the two side by side and ask: what new idea appears in the conclusion that the evidence does not mention? The assumption connects the two.
For example: "Residents of tree-lined streets report fewer heat-related illnesses than other residents, so planting trees reduces heat-related illness." The evidence is a difference between two groups; the conclusion says trees cause it. The assumption is that nothing else about the tree-lined streets explains the difference.
The negation test confirms an assumption. Negate the candidate and see whether the argument falls apart. "The tree-lined streets do not differ from others in any other relevant way" → negated: "the tree-lined streets are also wealthier, with more air-conditioned homes". Now the evidence no longer supports the conclusion, so the original statement was a necessary assumption. If the argument survives the negation, the candidate was not needed.
The usual gaps
Most flawed arguments make one of a few moves. Learning them by name lets you spot them fast.
| Gap | The move | What it ignores |
|---|---|---|
| Correlation to cause | A and B go together, so A causes B | a third factor; B causing A; coincidence |
| Sequence to cause | B followed A, so A caused B | anything else that changed at the same time |
| Unrepresentative sample | a group's view is taken as everyone's | that the group was chosen in a way that skews it |
| Past to future | what held before will hold again | changed conditions |
| Shifting term | a word means one thing in the evidence and another in the conclusion | that the evidence supports only the first meaning |
| Ruling out too little | one alternative is dismissed, so the favoured one must be true | other alternatives |
Describing a flaw
Flaw choices are written abstractly: "takes for granted that…", "fails to consider the possibility that…", "treats a correlation as proof of causation". Translate each into the argument's own terms before judging it. A choice may describe a real logical error that this argument does not commit; it must fit this argument. Name the gap yourself first, in plain words, and then look for the choice that describes it.
A routine
- Find the conclusion (indicators, then the "why?" test).
- List the evidence.
- Find what appears in the conclusion but not in the evidence: that is where the gap is.
- State the assumption that bridges it, or the flaw that ignores it, in your own words.
- Match a choice, and confirm an assumption with the negation test.
Worked examples
Example 1: Finding and testing an assumption
Over the past decade, the town of Ridgeford has planted trees along forty of its streets. Residents of the tree-lined streets report fewer illnesses related to summer heat than residents of other streets. The town council concludes that planting trees reduces heat-related illness, and it plans to plant trees along every street.
What does the council's conclusion assume?
Find the conclusion: "planting trees reduces heat-related illness". The plan follows from it. Ask "why believe it?": because residents of tree-lined streets report fewer heat illnesses. That is the evidence.
Compare them. The evidence is a difference between two groups of streets; the conclusion says the trees cause the difference. The new idea is causation, so the gap is correlation to cause.
State the bridge: the tree-lined streets do not differ from the other streets in some other way that would explain the difference, such as wealth, building type or the age of residents.
Negate it: "the tree-lined streets were chosen because they are in the town's wealthier districts, where most homes are air-conditioned". The evidence would then say nothing about trees, so the argument fails. The assumption is confirmed.
Answer
The council assumes that nothing other than the trees accounts for the lower rate of heat-related illness on tree-lined streets. A tempting wrong answer is "trees lower air temperature": that would help the argument, but the argument does not need it to be stated in those terms, and its negation does not destroy the conclusion on its own.
Example 2: An unrepresentative sample
A survey of the members of a city cycling club found that 85% of them support adding cycle lanes to the main avenue. The city's transport office concludes that most of the city's residents support the cycle lanes.
Describe the flaw.
Conclusion: most of the city's residents support the lanes. Evidence: 85% of a cycling club's members do.
What appears in the conclusion but not the evidence? "The city's residents" in general. The argument moves from one group to everyone.
Ask whether the group is likely to be typical. Members of a cycling club are chosen, by their own choice, for an interest in cycling, the very thing the question is about.
Answer
The argument generalises from a sample that is unlikely to represent the city's residents on this question. The tempting wrong description is "the sample is too small": the passage gives no size, and the problem is who was asked, not how many.
Common traps
Taking a reported view for the conclusion
"Some economists claim X. Yet… so Y." The first sentence is the view being argued against. If you take it for the conclusion, every assumption and flaw question on the argument will go wrong. Look for the author's own claim after the turn.
Assumptions that are too strong
A necessary assumption is the minimum the argument needs. "Morning meetings are the only way teams communicate" is far more than an argument about meetings needs; negate it ("there are other ways to communicate") and the argument is unharmed. Prefer the modest choice that the negation test confirms.
A real flaw, but not this argument’s
Flaw choices describe genuine errors in general terms. A choice can name a real mistake that the argument simply does not make: "relies on the opinion of experts" when no expert is mentioned. Translate the choice into the argument's terms before you accept it.
Check yourself
Answer each question before you open its answer.
Question 1: Assumption
Reading Comprehension: argument
A software company found that teams that held a short meeting every morning finished their projects on schedule more often than teams that did not. The company's director concluded that requiring all teams to hold a morning meeting will increase the share of projects finished on schedule.
The director's conclusion depends on which of the following assumptions?
- A.Morning meetings are the only way that members of a team communicate.
- B.Projects that are finished on schedule are of higher quality than those that are not.
- C.The teams that chose to hold morning meetings were not already better organised in ways that would by themselves explain their better record.
- D.Most teams in the company already hold a morning meeting.
- E.Meetings held in the afternoon would be less effective than morning meetings.
Show the answer
Answer: C. The teams that chose to hold morning meetings were not already better organised in ways that would by themselves explain their better record.
Working
The evidence is a correlation between choosing to hold morning meetings and finishing on schedule; the conclusion says requiring the meetings will improve the record, which treats the meetings as the cause. The argument needs the teams that chose meetings not to differ in some other way that explains their record. Negate that: if those teams were simply the better-organised ones, imposing meetings on others need not help, and the conclusion collapses.
Why the other options are wrong
- A. Far stronger than needed. Negate it, "teams also communicate in other ways", and the director's argument is unaffected.
- B. The conclusion is about finishing on schedule, not about quality; this is irrelevant to the reasoning.
- D. If anything this would limit how much a requirement could change; the argument does not need it.
- E. Afternoon meetings are never compared; the argument works whether or not they would help.
What carries over
When evidence compares groups that chose differently, the argument assumes the choice itself, not some trait of the choosers, explains the difference.
Question 2: Flaw
Reading Comprehension: argument
Last year the public library extended its weekday opening hours from 6 p.m. to 8 p.m. Over the same year, the number of books borrowed rose by 12%. Clearly, the longer opening hours were responsible for the rise in borrowing.
Which of the following describes a flaw in the reasoning?
- A.It draws a conclusion about all libraries from the experience of one.
- B.It confuses the number of visitors with the number of books borrowed.
- C.It assumes that every book was borrowed during the extended hours.
- D.It relies on the opinions of library staff rather than on records.
- E.It takes for granted that because the rise followed the change in hours, the change caused it, without considering other causes.
Show the answer
Answer: E. It takes for granted that because the rise followed the change in hours, the change caused it, without considering other causes.
Working
The evidence is that borrowing rose in the same year the hours were extended. The conclusion says the hours caused the rise. Nothing rules out other causes, such as new stock, a growing population or a reading campaign. That is the sequence-to-cause gap, which the choice about taking causation for granted describes.
Why the other options are wrong
- A. The conclusion is only about this library; no generalisation is made.
- B. Visitors are never mentioned; the argument speaks only of books borrowed throughout.
- C. The argument does not need this: longer hours could cause a rise even if only some extra borrowing happened in the evening.
- D. No opinions are cited; the 12% figure is presented as a count.
What carries over
When "clearly" introduces a cause drawn from two things that happened together, look for the alternatives the argument never ruled out.
Question 3: Main conclusion
Reading Comprehension: argument
Some economists claim that the arrival of railway lines caused the growth of market towns in the province of Esterra. Yet several Esterran towns were growing quickly before any line reached them, and a few towns that gained stations early grew hardly at all. The railway, it seems, sped up growth in towns that already had something to trade; it did not create that growth on its own.
Which of the following best states the main conclusion of the argument?
- A.The arrival of railway lines caused the growth of Esterra's market towns.
- B.Several Esterran towns were growing quickly before any railway line reached them.
- C.The railway accelerated growth in towns that already had trade but did not by itself create growth.
- D.Towns that gained stations early did not grow.
- E.Economists have overstated the importance of trade to Esterra's towns.
Show the answer
Answer: C. The railway accelerated growth in towns that already had trade but did not by itself create growth.
Working
Apply the "why?" test. The last sentence, that the railway sped up existing growth but did not create it, is supported by both facts in the middle sentence: towns grew before the railway, and some towns with early stations did not grow. Neither fact is supported by the last sentence, so the last sentence is the conclusion. The first sentence is the view being argued against.
Why the other options are wrong
- A. This is the economists' claim that the author argues against, introduced before the turn at "Yet".
- B. This is evidence; it answers "why believe the railway did not create growth by itself?"
- D. The passage says "a few" such towns grew hardly at all; this overstates a piece of evidence, and evidence is not the conclusion anyway.
- E. The author's claim makes trade more important, not less, and criticises the economists for overstating the railway.
What carries over
In an argument that opens with someone else’s claim, the conclusion is the author’s answer after the turn.
Key points
Find the conclusion with indicator words, then confirm it with the "why?" test.
The assumption bridges what is new in the conclusion and absent from the evidence.
Confirm an assumption by negating it: if the argument collapses, it was needed.
Name the gap in plain words before reading flaw choices, then match one that fits this argument.
All questions here are original and written for UniExamer; none comes from the test maker.
Written by the UniExamer team with AI assistance. Every worked example and check question was re-solved by an independent checker before publication. No subject expert has reviewed this lesson yet. If you find a mistake, write to support@uniexamer.com.