Identifying Assumptions

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Finding unstated premises that an argument depends on.

An assumption is an unstated belief that must be true for an argument to hold. Every argument rests on at least one assumption. Identifying assumptions is a core critical thinking skill because hidden premises can make an argument appear stronger than it actually is. By surfacing assumptions, you can evaluate whether the argument's foundation is solid or flawed.

Argument: P → C (assumes A); if A is false, P → C may not hold

• 'Sales rose after the ad campaign, so the campaign was effective.' Assumes: the sales increase was caused by the campaign, not by seasonal trends or other factors.
• 'This candidate has 20 years of experience, so they are the best choice.' Assumes: years of experience are the most important criterion for the role.
• 'Students who eat breakfast score higher on tests, so we should provide free breakfast.' Assumes: eating breakfast directly causes higher test scores.

How to recognize it

• Ask: 'What must be true for this conclusion to follow from the premises?'
• Look for gaps between the evidence presented and the conclusion drawn
• Check if the argument treats correlation as causation
• Identify any unstated link between the subject and the predicate

Common mistakes

• Confusing an assumption with a conclusion — the assumption is what is taken for granted, not what is argued
• Selecting a statement that is merely related to the topic rather than one the argument depends on
• Missing implicit causal assumptions when the argument jumps from correlation to causation

Practice guidance

Critical Thinking