CAT (Common Admission Test) · Verbal Ability & Reading Comprehension

Critical Reasoning

Testing CAT-density arguments: isolate the claim, name the gap, then strengthen, weaken, or assume.

Critical reasoning on CAT is the skill of testing a short argument — often one claim inside a longer VARC paragraph — by asking whether the evidence actually reaches the conclusion. You are not hunting grammar faults, idiom keys, or one-word substitutions. You isolate the claim the stem targets, name the unstated leap that would have to hold, and then decide whether a choice makes that leap safer, shakier, or simply names it.

CAT (Common Admission Test)
Hard level
6 concepts
12 practice questions

1Isolate the claim the stem hits

A CAT critical-reasoning stem, whether it sits on a short paragraph or on one sentence inside a longer RC, argues for one main claim. That claim is the conclusion: the sentence the rest of the paragraph is trying to justify. The supporting facts are premises. Background colour — a date, a side project, a visitor centre — is neither.

Most wrong answers attack a side fact, defend a different claim, or stay merely on-topic. If you have not named the exact conclusion, you cannot tell which choices miss it. Pin the conclusion first — the sentence the rest of the paragraph is trying to justify — before you open the options.

Figure. On the marsh-restoration stem, the city-wide bird-population claim is the conclusion. The 400-hectare restore is a premise; the visitor centre is colour a strengthen or weaken choice must not hit.

Label the argument

Spot the claimAsk which sentence the others try to justify. Cue words: therefore, so, thus, should, must — or the author's recommendation about a wider population.
List premisesMark the supporting facts as premises. They stay true on strengthen/weaken items unless a choice overturns one.
Park the colourSet aside dates, side projects, and scenery. A choice that only talks about those is not hitting the conclusion.

Pin the conclusion before the options

Argument: 'A district that installed streetlights on its main road saw night-time accidents fall for two years. A weekly market also opened on that road in year one. Streetlights therefore reduce night-time accidents in the district.' Which sentence is the conclusion that a strengthen or weaken stem must target?

'installed streetlights on the main road'a premise, the action taken, not the conclusion
'night-time accidents fell for two years'a premise, the observed effect, not the conclusion
'a weekly market opened in year one'background colour, park it
'streetlights therefore reduce night-time accidents'the claim the rest supports, the conclusion

Pro tip. The conclusion is the sentence the other lines justify, often flagged by therefore; an option that hits a premise or the scenery is aimed at the wrong target.

Paragraph: After the state restored 400 hectares of urban marsh, winter counts of resident waterbirds in those basins rose for two seasons. A visitor centre opened on the same site in year one. Restoration therefore increases resident waterbird populations in Indian cities. Which sentence is the conclusion a strengthen or weaken stem must hit?

After the state restored 400 hectares of urban marsh
Winter counts of resident waterbirds in those basins rose for two seasons
A visitor centre opened on the same site in year one
Restoration therefore increases resident waterbird populations in Indian cities

The last sentence is the claim the paragraph urges — a causal, city-wide generalisation. The restoration and the count rise are premises offered as support. The visitor centre is background colour. Treating either fact as the conclusion would make strengthen/weaken answers aim at the wrong target.

2The assumption is the necessary bridge

Premises rarely entail the conclusion by themselves. The missing link — an unstated idea that must hold for the premises to support the conclusion — is the assumption. State it in one blank sentence: this only works if ______. On the restored-marsh argument, the blank is some version of: the count rise is a real population rise caused by restoration, and those basins stand in for Indian-city marshes.

An assumption is needed by the leap; an inference is forced by the lines. CAT stems mix the two words. A choice that is true and topical but leaves the bridge untouched is a distractor. A choice that merely restates a premise is not an assumption — the paragraph already granted it.

Name the gap

Write C and PConclusion on one line; premises on the next. Leave a blank between them.
Fill the blankAsk what must be true for those premises to justify that conclusion. That sentence is the working assumption.
Sort the stemIf the stem says inferred or follows, keep only what the lines force. If it says assumes or depends on, keep only what the leap needs.

Same paragraph; two jobs. The criterion is whether a hostile reader must grant the choice from the stated lines, or whether the leap collapses without it.

Inference versus assumption
Job	What it must do	Classic miss
Inference	Follow from the stated lines; a hostile reader cannot deny it	A causal 'likely' the lines do not force
Assumption	Be needed for the leap; negate it and the argument dies	A helpful extra the author never required, or a restated premise

Argument: After marsh restoration, winter counts of resident waterbirds in the restored basins rose for two seasons. Therefore restoration increases resident waterbird populations in Indian cities. Which best names the unstated bridge?

Some walkers prefer the new boardwalk at weekends
The rise in counts reflects a real population increase caused by restoration, and the restored basins are typical enough of Indian-city marshes for that effect to generalise
Winter counts appear in a state wildlife report
Waterbirds pass through the region in October

The leap from a local count rise to 'restoration increases populations in Indian cities' needs both a real causal effect and a representative site. Weekend boardwalk taste, the existence of a report, and October passage are topical facts that do not bridge premise to conclusion.

3Negation finds a necessary assumption

On assumption stems, the correct choice is a claim the argument needs. The negation test finds it: negate the choice; if the argument collapses, the choice was necessary. If the argument still stands after negation, the choice was optional colour, not the bridge.

Necessary is stricter than helpful. A fact that would strengthen but is not required fails the test. Prefer the gap the premises leave open — representativeness, no rival cause, counts tracking populations — over a broad claim the author never needed.

Figure. Negate 'the restored basins represent Indian-city marshes'. If they do not, the leap from those winter counts to city-wide populations fails, so the assumption is necessary.

Negation test

State the gapWrite the one-sentence bridge before reading choices.
Negate each contenderForm the opposite: not representative, some other cause, counts do not track numbers on the ground.
Keep the breakerOnly the negation that makes the premises fail to support the conclusion is the required assumption.

The restored basins are representative of Indian-city marshes for this effect
Waterbirds are popular with weekend visitors
Restoration is cheaper than building new city parks
The visitor centre sold more tickets in year two

Negate A — the basins are not representative — and the leap to Indian cities fails. Negating visitor taste, relative cost, or ticket sales leaves that site-to-population bridge untouched; those are optional extras, not required assumptions.

4Weaken by opening a live rival path

A weakener makes the conclusion less likely while leaving the stated premises intact. The usual move is to break the assumption — often by offering an alternative cause for the same observed effect, a detectability story that explains the numbers without the claimed mechanism, or a counterexample the argument overlooked.

A choice that contradicts a premise outright is rarely needed. A choice that is merely related to the topic without touching the gap does not weaken. Pin the conclusion, then ask: which option opens a live alternative path to the same evidence?

Figure. A chemical plant that shut the month restoration began opens a rival cause for the count rise. Mud, recycled timber, and native grasses stay on-topic and do not break the restoration-as-cause bridge.

Weaken workflow

Lock conclusionRestate the exact claim you must make less likely — here, restoration increases resident waterbird populations in Indian cities.
Name the bridgeUsually: nothing else explains the effect, the measure tracks the real quantity, or the sample matches the target population.
Find the breakPrefer an alternative cause in the same window, a rival explanation of the measurement, or a case where premises hold and the conclusion fails.

Weaken by opening a rival path

Argument: 'After a district installed streetlights on its main road, night-time accidents fell for two years, so streetlights reduce night-time accidents there.' Which option most weakens it? (A) some drivers dislike the glare of the new lamps; (B) the district also lowered the night speed limit on that road the same month; (C) the lamps use energy-efficient LEDs; (D) the road was repaved a decade earlier.

lock the conclusionstreetlights caused the fall in night-time accidents
name the bridgenothing else explains the fall in the same window
test A glare, C LEDs, D old repavingon-topic but they leave the causal bridge intact, reject
test B, a simultaneous lower speed limita rival cause for the same fall, most weakens

Pro tip. A weakener leaves the premises intact and opens a live alternative path to the same evidence; a true but off-gap detail is not a weakener.

Argument: After the state restored 400 hectares of urban marsh, winter counts of resident waterbirds in those basins rose for two seasons. Therefore restoration increases resident waterbird populations in Indian cities. Which most weakens this?

Some walkers dislike muddy paths after rain
A nearby chemical plant that had been discharging into the same wetlands shut down the month restoration began
The visitor centre used recycled timber
Restoration crews planted native grasses

A simultaneous plant shutdown offers another cause for the count rise, so restoration-as-cause is less secure. Dislike of mud and recycled timber are on-topic and do not explain the rise. Native grasses, if anything, sketch a mechanism for the author's claim rather than opening a rival path.

5Strengthen by closing a hole, not restating

A strengthener makes the conclusion more likely without restating it. The usual move is to reinforce the assumption: rule out a rival cause, show the groups were comparable, hold survey effort fixed, or add evidence that the sample matches the population the conclusion names.

Do not confuse strengthen with assuming the conclusion. A choice that simply repeats the claim adds no new support. Ask whether the option closes a hole a weakener would have opened.

Figure. Same-city unrestored marshes with no winter rise close the everywhere-that-year rival. 'Restoration increases populations wherever tried' only restates the conclusion.

Strengthen workflow

Lock conclusionSame claim you would attack on a weaken stem — now you defend it.
List rivalsName the alternative causes, effort changes, or sampling gaps a hostile reader would raise.
Close one holePick the choice that rules out a rival or affirms a necessary condition — not a paraphrase of the conclusion.

Restoration increases resident waterbird populations wherever it is tried
Unrestored marshes in the same city, counted on the same winter schedule, showed no rise in those two seasons
Some restored basins still have patches of invasive weed
The visitor centre is popular with school groups

A same-city, same-schedule control with no rise closes the rival that birds increased everywhere that winter, so the restored-basin rise better supports restoration-as-cause. Option A restates the conclusion. Remaining weeds and a popular visitor centre do not defend the causal or scope bridge.

6Causal leaps and scope shifts

Many CAT-density arguments move from A happened, then B changed to A caused B, or from one district, panel, or season to a nation, a population, or 'in general'. That leap assumes no rival cause, no reverse causation, and a sample that matches the target on the traits that matter for the effect. A time order alone is not proof of cause.

Spotting the gap tells you what weakeners and strengtheners must do. A weakener often names a simultaneous change, a detectability story, or a relevant mismatch of place, people, or time. A strengthener often shows the effect appears when the rival is absent, or that the measured group matches the group in the conclusion. Do not treat a true off-gap detail as a hit.

Scope and cause check

Name both endsWho or what was measured, and whom does the conclusion claim to cover? What changed, and what is said to have caused it?
List the leapsCorrelation to cause; sample to population; one season to always; one city to Indian cities.
Act on the stemAssume the match and the missing rival; strengthen by affirming them; weaken with a relevant mismatch or a live alternative cause.

The same restored-marsh or night-bus leap can be attacked or defended. The criterion is whether the choice touches cause or scope, not whether it is true of the topic.

Causal and scope moves
Stem job	What to look for	Classic miss
Weaken a causal leap	Rival cause in the same window, reverse cause, or a measurement that can rise without the claimed effect	A true but off-gap fact about the topic
Strengthen a causal leap	Rival ruled out, groups matched beforehand, or a control with no change	Restating that A caused B
Assumption on cause or scope	No other cause explains B, or the sample matches the target on traits that could change the result	A helpful detail the argument does not need

Argument: Districts that adopted a night-bus corridor later recorded higher women's workforce participation. Therefore night buses cause that rise. Which most weakens this?

Night buses on the corridor are painted teal
The same districts also opened 24-hour crèches and expanded safe night housing the same year
Some riders complain about frequency at the last stop
The corridor uses electric buses

Crèches and safe housing are simultaneous changes that can explain the participation rise, so night-buses-as-cause is weakened. Paint colour, a frequency complaint, and electric traction do not supply an alternative cause for the labour-force change.

Notes

Isolate the conclusion first: The conclusion is the sentence the rest of the paragraph is trying to justify; the supporting facts are premises, and background colour is neither. Most wrong options attack a side fact or defend a different claim.
The assumption is the necessary bridge: Premises rarely entail the conclusion by themselves, so state the missing link as one blank sentence - this only works if ____. An assumption is needed by the leap while an inference is forced by the lines, and a restated premise is neither.
Negation finds a necessary assumption: Negate a candidate; if the argument collapses, the claim was required, and if the argument still stands, the choice was optional colour. Necessary is stricter than merely helpful.
Weaken by opening a live rival path: A weakener leaves the stated premises intact and makes the conclusion less likely - an alternative cause for the same effect, a measurement that can rise without the mechanism, or a relevant scope mismatch. Being on-topic is not weakening.
Strengthen by closing a hole: A strengthener rules out a rival cause, shows the groups were comparable, holds the survey effort fixed, or shows the sample matches the population the conclusion names. Repeating the conclusion adds no support.
Causal and scope leaps: Moving from "A happened, then B changed" to "A caused B", or from one district or season to a whole population, assumes no rival cause, no reverse causation, and a sample that matches on the traits that matter. Time order alone is not proof of cause.

Formulas

Find the conclusion first: it is the sentence the rest of the paragraph justifies. Premises support it; background colour does neither.
State the assumption as one blank sentence — this only works if ____. An assumption is needed by the leap; an inference is forced by the lines.
Negation test: negate the candidate. If the argument collapses the assumption was necessary; if it still stands, the choice was optional.
Weaken by opening a live rival path — an alternative cause, a measure that can move without the mechanism, or a scope mismatch — while leaving the premises intact.
Strengthen by closing a hole: rule out a rival cause, show the groups were comparable, hold the survey effort fixed, or match sample to population.
Causal and scope leaps assume no rival cause, no reverse causation, and a sample matching the population named. Time order alone is not proof of cause.

Exam traps & shortcuts

Options that attack a side fact feel aggressive and change nothing. Locate the conclusion before judging any of them.
A restated premise is neither an assumption nor an inference, and it is the most common wrong answer on assumption stems.
Necessary is stricter than helpful: negate the candidate and see whether the argument actually collapses.
A weakener must leave the premises intact. An option that denies a stated fact is out of scope, not a weakener.
Time order is not causation. On any "A then B, so A caused B" argument, look first for a rival cause and for reverse causation.

Reference tables

Night-before sheet for CAT-style critical reasoning. Read the stem's verb before the options. The same restored-marsh paragraph can be a weaken, strengthen, or assumption item; the job changes, the gap does not.

Stem jobs
Stem cue	Your job	Do not
most weakens / undermines	Open a live rival path to the same evidence	Contradict a stated premise for sport, or pick a true off-gap fact
most strengthens / supports	Close a hole a hostile reader would open	Repeat the conclusion in more confident words
assumes / depends on	Name the necessary bridge; negate to confirm	Pick a fact that would merely help, or a restated premise
inferred / follows	Keep only what the stated lines force	Import a cause or a wider population the paragraph never stated

Recap

Read only this the night before a CAT VARC sitting.

Conclusion first: Name the exact claim the stem hits before opening options. Side facts and scenery are not the target.
Bridge: An assumption is needed by the leap; an inference is forced by the lines. CAT stems mix the words.
Negation: Negate the choice. If the argument still stands, the choice was optional colour, not the required assumption.
Weaken: Leave the premises intact and open a live rival path — other cause, detectability, or a relevant scope mismatch.
Strengthen: Close a hole. A paraphrase of the conclusion adds no support.
Cause and scope: A time order alone is not proof of cause. One basin, district, or season is not automatically Indian cities.

Practise Critical Reasoning

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