Logical Reasoning
What this domain tests
Logical reasoning tests deductive validity, conditional statements, quantifiers, assumptions, and argument evaluation. Most stimuli are short, so precision matters more than speed. The exam asks what must follow, not what is plausible in the real world.
Core rules
- For a conditional 'If P, then Q', the valid inferences are P implies Q and not-Q implies not-P. 'Not-P implies not-Q' and 'Q implies P' are invalid.
- 'All A are B' does not imply 'All B are A'; 'some' means at least one and does not guarantee overlap beyond what is stated.
- In strengthen or weaken questions, attack the link between evidence and conclusion, not the conclusion's popularity.
- For ordering and grouping, draw a grid and record fixed positions; eliminate duplicated options.
Worked example
If a proposal is approved, the budget increases. The budget did not increase. What follows? The valid conclusion is that the proposal was not approved. This is the contrapositive of the conditional. Concluding that the proposal was rejected for political reasons adds a cause not stated in the stimulus.
Traps
- Affirming the consequent: 'The budget increased, so the proposal was approved' is invalid.
- Denying the antecedent: 'The proposal was not approved, so the budget did not increase' is invalid.
- Treating 'some' as 'most' or 'all'.
- Choosing an answer that is true in the real world but unsupported by the stimulus.
- In assumption questions, selecting a restatement of the evidence rather than a necessary bridge.