Reverse Syllogism
Reverse Syllogism (also called Reverse Syllogism or Backward Syllogism) presents a conclusion and several sets of premises. You must identify which set of premises logically leads to the given conclusion. These problems test your ability to work backwards and recognize valid syllogistic patterns.
What You'll Learn
Introduction to Reverse Syllogism
Reverse Syllogism (also called Reverse Syllogism or Backward Syllogism) presents a conclusion and several sets of premises. You must identify which set of premises logically leads to the given conclusion. These problems test your ability to work backwards and recognize valid syllogistic patterns.
Prerequisites
How to Solve Reverse Syllogism Problems
Step 1: Read the given conclusion carefully
Step 2: For each premise option, check if the conclusion can be derived
Step 3: Apply syllogism rules in reverse: think about what premises would produce this conclusion
Step 4: For 'All A are C' conclusion, possible premise pairs: (All A are B, All B are C) or (All A are B, No B is C? No - that gives No A is C)
Step 5: For 'No A is C' conclusion, possible premise pairs: (All A are B, No B is C) or (No A is B, All B are C)
Step 6: For 'Some A are C' conclusion, possible premise pairs: (All A are B, Some B are C) or (Some A are B, All B are C)
Step 7: Verify the valid option(s) and select the correct answer
Example Problem
Example: Given Conclusion: Some A are C. Which set of statements leads to this conclusion? Options: A. All A are B; All B are C. B. Some A are B; All B are C. C. No A is B; Some B are C. D. All A are B; No B is C. Solution: Step 1: Conclusion: Some A are C Step 2: Option A: All A are B + All B are C = All A are C (not Some) → NO Step 3: Option B: Some A are B + All B are C = Some A are C → YES Step 4: Option C: No A is B + Some B are C = Some C are not A (not Some A are C) → NO Step 5: Option D: All A are B + No B is C = No A is C → NO Answer: Option B (Some A are B; All B are C)
Pro Tips & Tricks
- All A are C ← (All A are B, All B are C) or (All A are B, Some B are C? No, that gives Some A are C)
- No A is C ← (All A are B, No B is C) or (No A is B, All B are C)
- Some A are C ← (All A are B, Some B are C) or (Some A are B, All B are C)
- Some A are not C ← (All A are B, Some B are not C) or (Some A are B, No B is C)
- Test each option systematically
- Use Venn diagrams to verify
Shortcut Methods to Solve Faster
Common Mistakes to Avoid
Practice Worksheets
Practice makes perfect! Work through these worksheets to master Reverse Syllogism. Each worksheet contains 20 questions with detailed explanations. Start from Worksheet 1 and progress through increasing difficulty levels.
Exam Importance
Reverse Syllogism is an important topic for various competitive exams. Here's how frequently it appears:
Ready to Master Reverse Syllogism?
Start with Worksheet 1 and work your way up to expert level! Each worksheet includes: