Unless
LSAT glossary · Logical Reasoning
Definition
An LSAT conditional indicator that introduces a necessary condition, equivalent to "if not." "A unless B" translates to ¬B → A (and equivalently ¬A → B): without B, A must occur — B is the necessary condition that prevents A. Example: "You can't drive unless you are at least sixteen" translates to drive → at least 16. The "Unless" Mantra is to negate the "unless" clause and place the remainder on the sufficient side.
Unless in plain English
In everyday speech 'unless' means 'if not' — 'I'll be late unless I hurry' really says 'if I don't hurry, I'll be late.' So the thing after 'unless' is the required ingredient that keeps the bad outcome away. 'You can't drive unless you're at least sixteen' means being sixteen is the necessary condition — if you ARE driving, you must be sixteen (drive rightarrow at least 16). The tutor's trick: negate whatever follows 'unless,' and put the rest on the 'if' side.
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Practice Unless
The reasoning in the argument is flawed because the argument
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