Master Critical Reasoning Assumptions

Assumption questions typically make up 15-20% of Critical Reasoning questions in CAT VARC. Given that CR usually has 12-16 questions across the section, expect 2-3 assumption questions per CAT exam.

These questions are identifiable by phrases like “assumes that”, “depends on the assumption”, “presupposes which of the following”, “relies on which assumption”, or “reasoning requires assuming”. The exact wording varies but the task remains constant: find the unstated idea the argument needs to work.

While percentage-wise they’re less common than strengthen/weaken or inference questions, assumption questions are critical because they test pure logical structure. They reveal whether you understand how arguments are built and where their weaknesses lie. Strong performance on assumption questions often predicts strong CR performance overall because the skill transfers—spotting gaps and bridges helps with every question type.

Use a streamlined 3-step approach: identify the conclusion (15 seconds), spot the gap between premises and conclusion (20 seconds), apply negation test to most promising options (30 seconds). This gives you 65 seconds per question, which is sustainable even with 4 options to evaluate.

The key efficiency gain comes from prediction before evaluation. Don’t read all four options and try to judge each independently. Instead, after identifying the gap, predict what kind of assumption fills it:

• Causal gap needs “no other causes” or “cause is sufficient”
• Plan gap needs “no major obstacles” or “plan is feasible”
• Comparison gap needs “things are comparable”
• Survey gap needs “sample represents population”

With prediction locked, scan options for matches. You’ll often find one or two options that obviously don’t address the gap—eliminate these in 5 seconds. Then negation test the remaining candidates.

Necessary assumptions are required for the argument to hold—without them, the conclusion doesn’t follow. Sufficient assumptions, if true, guarantee the conclusion follows—they’re strong enough to make the argument work completely. CAT focuses almost entirely on necessary assumptions.

The negation test identifies necessary assumptions: negate the statement, and if the argument collapses, it’s necessary. Sufficient assumptions are tested differently: assume the statement is true, and check if the conclusion must follow with no remaining gaps. Sufficient assumptions are typically much stronger claims than necessary ones.

In CAT-style questions, correct answers are necessary assumptions phrased carefully to be true enough for the argument but not overkill. Options phrased as sufficient assumptions are usually traps—they’re stronger than needed and often include “only”, “sole”, “exclusively”, or “always”.

Pro Tip: If an option makes the argument seem completely airtight and you think “if this were true, the conclusion is definitely correct”, it might be sufficient rather than necessary. Check whether the argument could limp along without it. Necessary assumptions are minimum requirements, not ideal conditions.

Strengtheners make the argument better by adding supporting evidence. Assumptions are requirements the argument already depends on, whether stated or not. The confusion happens because both help the argument, but strengtheners are optional additions while assumptions are non-optional foundations.

Test the distinction with the negation approach. If you negate a strengthener, the argument gets weaker but doesn’t collapse. It still limps along because it wasn’t depending on that statement. If you negate an assumption, the argument falls apart because it was built on that foundation even though the foundation wasn’t visible.

The trap works because strengtheners feel relevant and helpful. When you’re reading options under time pressure, “this makes sense and helps the argument” feels correct. But assumption questions demand higher standards: “this must be true for the argument to work at all.”

Pro Tip: After picking an answer, ask yourself: “Did the author secretly need to believe this for the argument to make sense?” If yes, it’s assumption. “Would this additional fact make the argument more convincing?” If yes but not required, it’s strengthener.

The negation test is systematic: take the statement, create its reasonable opposite, and check if the argument survives. The opposite should be proportional—don’t make extreme negations, just flip the core claim.

Step 1: Identify the main claim in the option.
Option: “Most customers prefer the new design.” Main claim: majority preference for new design.

Step 2: Create proportional opposite.
Don’t negate to “No customers prefer new design” (too extreme). Negate to “Most customers don’t prefer the new design” or “Customers are split/prefer the old design.”

Step 3: Insert negation into argument context.
Reread the conclusion while assuming the negation is true. Does the conclusion still follow from the premises? Does it become questionable? Does it fail completely?

Step 4: Make your judgment.
If conclusion fails or becomes seriously questionable, the original statement is a necessary assumption. If conclusion still has reasonable support, the statement isn’t necessary.

Pro Tip: If you’re unsure whether negation breaks the argument, ask “Could both the premises and the negation be true while the conclusion is false?” If yes, the option is a necessary assumption.

When two options both seem to damage the argument when negated, you need a tiebreaker strategy. Choose the option that targets the core premise-conclusion link rather than side issues or background conditions.

Tiebreaker 1: Which option addresses the main logical gap?
Arguments typically have one major leap from premises to conclusion. The assumption that bridges this leap is more necessary than assumptions about surrounding details.

Tiebreaker 2: Which option does the argument more directly depend on?
Some options are background conditions that would help but aren’t part of the argument’s logical flow. Others are integral to the reasoning chain. The argument “depends on” the second type more directly.

Tiebreaker 3: Which option is stated more conservatively?
Between two seemingly necessary assumptions, the one with moderate language (“some”, “generally”, “often”) is more likely correct than one with extreme language (“all”, “only”, “never”). Necessary assumptions operate at minimum threshold.

Pro Tip: The correct assumption in multi-candidate scenarios usually connects most directly to the conclusion’s key claim. If the conclusion claims causation, pick the assumption about causal attribution. Match assumption type to conclusion type.

Build a mental checklist that separates them by direction, presence, and function. Assumptions go backward from conclusion and are unstated. Inferences go forward from premises and are derivable.

Direction test: Ask “Is this needed for the conclusion (assumption) or does it follow from the premises (inference)?” Assumptions support the conclusion from below. Inferences extend from the premises.

Presence test: Ask “Does the passage prove this or does the passage need this?” If the passage proves it by establishing relevant facts, it’s inference. If the passage needs it to be true but doesn’t establish it, it’s assumption.

Function test: Ask “Does this fill a gap (assumption) or extend the logic (inference)?” Assumptions bridge between premises and conclusion where connection isn’t explicit. Inferences take what’s established and draw further conclusions.

Pro Tip: In practice questions, mark every assumption question with “A” and every inference question with “I”. After reviewing answers, check if you picked inference-type statements for assumption questions or vice versa. If you did this more than twice in a set of 10 mixed questions, you need to drill the distinction explicitly with 20 focused questions.