Flawed Parallel ReasoningDiff: Hardest
Logic Breakdown
Passage Summary: If you want your deposit to count for today, you have to get it in before 3 P.M. Alicia knows she made it in time, so she concludes she knows it was credited today.
Conclusion: Alicia knows that the bank deposit was credited on the date of the transaction.
Reasoning: Deposits are only credited on the same day if they occur before 3 P.M., and Alicia knows the deposit was made before that time.
Analysis: This argument is a double-decker bus of logical failure. First, it commits a classic conditional error by treating a necessary condition (being before 3 P.M.) as a sufficient one; just because you must be early doesn't mean being early guarantees success. Second, it makes an illicit leap regarding 'knowledge'—just because Alicia knows the premise is true doesn't mean she automatically knows the conclusion is true. When looking for a parallel, find a choice that mistakes a requirement for a guarantee and assumes a character's awareness of the facts translates to awareness of the outcome.
Conclusion: Alicia knows that the bank deposit was credited on the date of the transaction.
Reasoning: Deposits are only credited on the same day if they occur before 3 P.M., and Alicia knows the deposit was made before that time.
Analysis: This argument is a double-decker bus of logical failure. First, it commits a classic conditional error by treating a necessary condition (being before 3 P.M.) as a sufficient one; just because you must be early doesn't mean being early guarantees success. Second, it makes an illicit leap regarding 'knowledge'—just because Alicia knows the premise is true doesn't mean she automatically knows the conclusion is true. When looking for a parallel, find a choice that mistakes a requirement for a guarantee and assumes a character's awareness of the facts translates to awareness of the outcome.
Passage Stimulus
Passage Redacted
Unlock Full Passage21.Which one of the following exhibits both of the logical flaws exhibited by the argument above?
Correct Answer
C
C matches both errors. It treats “George will be promoted only if Helen resigns” (Promoted → Helen resigns) as though Helen’s resignation would guarantee promotion (a mistaken reversal), and it concludes that George knows he will be promoted merely from his knowing that Helen will resign, without establishing that he knows a rule that would validly lead to that knowledge.
Upgrade Your Prep
Ready to go beyond free explanations?
LSAT Perfection is the #1 modern LSAT prep platform, trusted by thousands of students for comprehensive test strategies, advanced drilling, and full analytics on every PrepTest.
Detailed explanations for 59 PrepTests
Advanced drillset builder
Personalized analytics
Built-in Wrong Answer Journal