How to solve: Conditional Reasoning
What this category tests
Tests deductive reasoning specifically about "if-then" statements — distinguishing necessary conditions from sufficient ones, validly chaining conditionals together, and telling the logically valid contrapositive apart from the invalid converse or inverse.
Where this typology comes from
Conditional logic was systematized by the Stoic logician Chrysippus around the 3rd century BCE — his first two "indemonstrable" argument forms are exactly modus ponens and modus tollens, the backbone of this category. The format is also closely associated with the Logical Reasoning section of the LSAT, first administered in 1948 by a consortium of U.S. law schools, where conditional-statement questions have long been a hallmark of the exam.
How to approach it
Translate every conditional into a strict 'if P, then Q' form before reasoning about it. Always feel free to derive the contrapositive ('if not Q, then not P') — it's logically guaranteed to be true whenever the original is. But never assume the converse ('if Q, then P') or the inverse ('if not P, then not Q') — both are classic invalid inferences, even though they feel intuitive. When chaining several conditionals together, double-check that each one's consequent exactly matches the next one's antecedent.
Worked example
Rule: 'If a shipment is marked fragile, then it is wrapped in bubble wrap.' A shipment on the loading dock is NOT wrapped in bubble wrap. What can you validly conclude?
- The shipment is not marked fragile ✓ Correct answer
- The shipment is marked fragile
- Nothing can be concluded about whether it's marked fragile
- The shipment was wrapped incorrectly
Explanation The rule says fragile implies bubble-wrapped. This shipment is not bubble-wrapped, so by the contrapositive — 'if not bubble-wrapped, then not fragile' — it cannot be marked fragile. This is a valid modus tollens inference, not a guess.
Practice Conditional Reasoning
- Conditional Reasoning I · 12 questions · Difficulty 3 out of 5
- Conditional Reasoning II · 12 questions · Difficulty 3 out of 5
- Conditional Reasoning III — Parallel Reasoning · 12 questions · Difficulty 4 out of 5
- Conditional Reasoning IV — Necessary & Sufficient Assumptions · 12 questions · Difficulty 4 out of 5