Syllogism
About 6 min · Reasoning Ability · English
Time worked out from the lesson's 398 words at 150 words a minute, plus a minute for each question.
These questions test your ability to draw valid logical conclusions from two given statements using universal and particular quantifiers (All, Some, No, Only).
Key ideas
- Universal Positive (A-type): "All A are B" — Every member of A belongs to B. A is completely inside B.
- Universal Negative (E-type): "No A is B" — Not a single member of A belongs to B. A and B don't overlap at all.
- Particular Positive (I-type): "Some A are B" — At least one member of A belongs to B. Partial overlap exists.
- Particular Negative (O-type): "Some A are not B" — At least one member of A does not belong to B.
- "Only A are B" = "All B are A": This is a critical conversion. "Only teachers are graduates" means "All graduates are teachers."
Watch out for
- "All A are B" means "All B are A" → WRONG. "All A are B" only guarantees "Some B are A." Always remember A is the subset, not B.
- Drawing only one Venn diagram → WRONG when checking definite conclusions. A conclusion is definite only if it's true in EVERY possible valid diagram. Draw multiple configurations.
- Confusing "Only" with "All" → "Only A are B" means "All B are A," not "All A are B." Flip the subject and predicate.
Quick reference
- All A are B → Some B are A (always valid conversion)
- No A is B = No B is A (symmetric relationship)
- Only A are B = All B are A (swap and change to All)
- Two negatives or two particulars = No definite conclusion
- Possibility = True in at least one valid diagram; Definite = True in all valid diagrams
Check yourself: 3 questions
1. Statements: All flowers are plants. All plants are trees. Conclusions: I. All flowers are trees. II. Some trees are flowers.
2. Statements: Some books are pens. No pen is pencil. Conclusions: I. Some books are not pencils. II. No book is pencil.
3. Statements: Only a few doctors are engineers. All engineers are professors. Conclusions: I. Some doctors are professors. II. All doctors being professors is a possibility.
This lesson is cut from the topic's note, not rewritten. Fact-checked on 18 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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