Introduction

This guide covers the Syllogism topic for CHSL aspirants. Master the concept, understand the tricks, and then test yourself with 10 practice MCQs.

Syllogism — Concept Guide

Syllogism is a form of deductive reasoning where a conclusion is drawn from two given statements (premises). In competitive exams, you are given statements and asked whether conclusions logically follow.

Types of Statements

  • Universal Affirmative (A): All A are B
  • Universal Negative (E): No A is B
  • Particular Affirmative (I): Some A are B
  • Particular Negative (O): Some A are not B

Key Rules

  • All A are B + All B are C → All A are C (✓ valid)
  • Some A are B + All B are C → Some A are C (✓ valid)
  • Some A are B + Some B are C → Some A are C (✗ NOT valid)
  • No A is B + All B are C → No A is C (✓ valid)
  • Conversion: "All A are B" does NOT mean "All B are A"

⚡ Shortcuts & Tricks

  • Draw Venn diagrams to visualise: circles inside circles or overlapping/separate.
  • "Some" is the weakest connector — avoid strong conclusions with it.
  • If both premises are particular (Some…Some), NO definite conclusion follows.
  • If one premise is negative, the conclusion must be negative.
  • Universal negative is symmetric: "No A is B" = "No B is A".
  • For "Either-or" conclusions: check if both conclusions are individually false.

Practice MCQs — Syllogism (10 Questions)

Now test your understanding with these 10 questions:

Q1. All cats are dogs. All dogs are horses. Conclusion: All cats are horses.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — If All A are B, and All B are C, then All A are C. Valid syllogism.

Q2. Some fruits are vegetables. All vegetables are food. Conclusion: Some fruits are food.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — Some fruits → vegetables → food. So some fruits are food. TRUE.

Q3. No cow is a bird. All birds can fly. Conclusion: No cow can fly.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: C — Some birds can fly, and cows are not birds. But we cannot conclude no cow can fly definitively without more info.

Q4. All men are mortal. Socrates is a man. Conclusion: Socrates is mortal.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — Classic syllogism: All A are B. X is A. Therefore X is B. TRUE.

Q5. Some A are B. Some B are C. Conclusion: Some A are C.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: C — This conclusion does NOT necessarily follow from the premises.

Q6. All roses are flowers. No flower is a tree. Conclusion: No rose is a tree.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — All roses are flowers, no flower is a tree → No rose is a tree. TRUE.

Q7. Some pens are books. All books are tables. Conclusion I: Some pens are tables. Conclusion II: All tables are books.

  • A. Only I follows
  • B. Only II follows
  • C. Both follow
  • D. Neither follows
Answer: A — Conclusion I: Some pens → books → tables. TRUE. Conclusion II: Converse of universal is not valid. FALSE.

Q8. All cups are plates. All plates are bowls. Conclusion: All cups are bowls.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — Transitive: All A→B, All B→C → All A→C. TRUE.

Q9. No teacher is a student. Some students are intelligent. Conclusion: Some intelligent people are not teachers.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — Some students are intelligent & no teacher is a student → some intelligent are not teachers.

Q10. All fish live in water. Shark is a fish. Conclusion: Shark lives in water.

  • A. True
  • B. False
  • C. Uncertain
  • D. Cannot say
Answer: A — Classic syllogism. TRUE.

Summary

Syllogism is a scoring topic in CHSL if you practise consistently. Focus on understanding the concept, apply the shortcut tricks, and practice regularly. Aim for 100% accuracy in this topic through regular revision.