Unit 8 · Detecting Reasoning Errors
Stolen Money — Contrapositive Error
Lesson 10 of 34
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About this lesson
A single "whoever did X must have Y and Z" rule looks simple — but it generates exactly one valid family of conclusions. The rest are traps dressed as logic.
Chapters
0:00Introduction
0:22Question
1:01Strategy
1:54Step 1: Write the rule as arrows — and learn the two valid moves
2:47Step 2: Test each option — find the valid one
3:56Correct answer
Question
"Whoever stole the money must have had both an opportunity and a motive."
If this is true, which one of these sentences must also be true?
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