Critical Reasoning — Explained
Detailed Explanation
What makes a group of sentences an argument?
An argument offers one or more reasons for accepting a conclusion. A description simply reports what happened. “The town added buses and opened a terminal” is a description. “The town should add buses because existing services are overcrowded” is an argument: the recommendation is supported by a claim about demand. Words such as therefore and because can help identify the roles, but their absence does not mean no argument exists.
Find the conclusion by asking what the speaker wants the reader to accept. Then ask which statements are offered in support. A passage can contain background information, an opponent's view and a counterargument. Do not assume that its last sentence is always the conclusion or that the longest sentence carries the main claim.
Where is the reasoning gap?
Consider this invented argument: “A library's digital borrowing increased during a free trial. The library should therefore replace all printed lending with digital lending.” The evidence concerns increased use of one service during a trial. The conclusion concerns replacing another service permanently. Missing links include whether users can access digital devices, whether printed borrowing meets different needs and whether the trial price influenced demand.
The question may target only one of these links. An assumption question asks for a required bridge; a weakening question asks for information that reduces the conclusion's support. A statement that merely discusses libraries is not automatically relevant. It must change the connection between the particular evidence and the particular recommendation.
How does strengthening work?
Strengthening adds support without necessarily proving the conclusion. Suppose an invented council argues that extending bus hours will help late-shift workers because current services end before their shifts. Evidence that many affected workers live along the proposed routes supports the practical link. Evidence that the buses will be painted a popular colour does not address whether the workers can use them.
A useful strengthener may rule out an alternative explanation, confirm that a sample is representative, establish feasibility or support an assumed causal mechanism. Its relevance depends on the argument. The same fact can strengthen one recommendation and weaken another. Identify the conclusion before deciding whether a detail is favourable.
How does weakening differ from contradiction?
A weakener need not deny a stated premise. In the digital-library example, “many users cannot access a suitable device outside the library” can weaken the replacement proposal while leaving the increase in digital borrowing entirely true. It challenges the move from trial uptake to universal replacement.
An option that contradicts a premise may be unsuitable if the question asks for additional information consistent with the passage. More often, the strongest weakener exposes an overlooked condition or alternative cause. If crop yields rose after both irrigation and a new seed variety were introduced, the second change weakens a claim that irrigation alone explains the improvement. It does not prove irrigation had no effect.
Why do samples and denominators matter?
An invented survey of 100 regular train passengers finds that 80 favour later trains. That result describes the surveyed group. It may not represent people who currently avoid trains because stations are inaccessible. A recommendation about all commuters requires attention to who was sampled and who was excluded.
Rates also matter. Suppose reported defects fall from 20 to 15 while production falls from 1,000 to 500 units. The defect count fell, but the defect rate rose from 2 percent to 3 percent. A claim that quality improved based only on the lower count is weakened by the denominator. Write the numerator and denominator explicitly before evaluating claims about performance.
How should conditional claims be assessed?
“A permit is issued only after inspection” means inspection is necessary for a permit. It does not mean inspection guarantees a permit. A claim that an inspected site must have permission reverses the relation. Conversely, if every issued permit satisfies the inspection rule and a site has a permit, inspection follows within the stated premises.
Do not add an existence claim without support. “All qualifying vehicles pass the emissions test” does not establish that any vehicle qualifies. Formal reasoning works with the information given, not with the everyday expectation that a category probably contains members. For practical prose, preserve the author's qualifications rather than replacing them with an absolute rule.
What makes a useful explanation of an answer?
An answer explanation should name the conclusion, identify the gap and show how the selected option affects that gap. “This is relevant” is insufficient. For the device-access weakener, the explanation is that a policy replacing print relies on digital access being adequate for the users who would lose the printed service.
Review distractors by their function: irrelevant background, repeated premise, alternative cause, changed population or unsupported extreme claim. A repeated premise may sound persuasive but add no new support. A dramatic fact about a different population may add none either. The most efficient solver checks argument structure before judging the emotional or topical appeal of the options.