Logic and Critical Reasoning
Core concepts
Expect deductive validity, syllogisms, conditional reasoning (if–then, contrapositive), necessary vs sufficient conditions, inductive strength, and fallacy identification (ad hominem, straw man, false dilemma, circular reasoning). Candidates must distinguish truth from validity and detect assumptions and conclusions in arguments.
Traps
The classic trap is affirming the consequent ("If P then Q; Q; therefore P" - invalid) and denying the antecedent. Another is confusing correlation with causation. Distractors may be true statements that do not follow from the premises.
Worked example / rule of thumb
Rule: the only valid conditional inferences are modus ponens (P→Q; P; ∴ Q) and modus tollens (P→Q; not Q; ∴ not P). Example: "If it rains, the ground is wet. The ground is not wet. Therefore it did not rain." - Valid (modus tollens). But "The ground is wet, therefore it rained" is invalid (affirming the consequent).
Strategy
Identify premises and conclusion, then test the form, not the content.