Find the argument’s dependency
Evaluate causal claims and necessary assumptions.
The idea
Locate the conclusion and the evidence. A new fact weakens a causal argument when it supplies an alternative explanation; an assumption is necessary when denying it breaks the reasoning.
A method to try
- Summarise the conclusion in one sentence.
- Identify what must connect the evidence to the conclusion.
- Choose a direct logical effect over a merely related fact.
Follow the reasoning.
A shop offers home delivery and sales rise the same month that a nearby competitor closes. What limits the conclusion that delivery caused all of the increase?
- The competitor’s closure gives customers another reason to move purchases to the shop. It is an alternative explanation for at least some of the sales change.
- The point is not that delivery had no effect. The evidence does not separate its contribution from the other change, so attributing the entire increase to delivery goes beyond the data.
- When evaluating arguments, distinguish a challenge to certainty from proof of the opposite conclusion. A weakening fact can reduce support without conclusively disproving the claim.
Think it through first.
A proposal predicts profit will rise because revenue will rise. What additional quantity must be considered?
Show the explanation
Costs.
Profit depends on revenue minus costs; an even larger cost increase could defeat the prediction.
Make it your own
After reading, explain the method in your own words and identify the condition that makes it valid. Then try the linked starter practice without referring back to the worked example. Review the reasoning behind an error before repeating the same item; remembering an answer is different from being able to solve a new problem.
This lesson is one part of a short starter pathway. It does not cover the full exam syllabus or establish a predicted score.
Official references
These provider and publisher links explain the exam or underlying concepts. Our lessons and questions are original, independent practice.
View 4 references and checked dates
- GMAC: exam structure (opens in a new tab)Checked 2026-10-06
- GMAC: exam content (opens in a new tab)Checked 2026-10-06
- GMAC: official preparation (opens in a new tab)Checked 2026-09-20
- GMAC: calculator and note-taking policies (opens in a new tab)Checked 2026-10-06