Only If
LSAT glossary · Logical Reasoning
Definition
An LSAT conditional indicator that introduces a necessary condition: "A only if B" translates to A → B (B is necessary for A). This is the single most commonly confused conditional translation — many test-takers misread "only if" as "if," reversing the arrow. Example: "You can enter the club only if you have a membership card" means enter → card; having a card is necessary, but does NOT guarantee entry. The rule: "only" introduces the necessary condition, never the sufficient.
Only If in plain English
'Only if' points to what's REQUIRED, not what's enough — and that trips up almost everyone, because it looks like plain 'if.' 'You can enter the club only if you have a card' means having a card is necessary to get in (enter rightarrow card), but a card alone doesn't guarantee they'll let you in. Think of it as a gate you must pass through, not a golden ticket. Rule of thumb: the word 'only' always tags the necessary condition — the arrow points toward it, never away.
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Practice Only If
Which one of the following can be properly inferred from these statements?
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