Syllogism Questions for SSC CHSL

Types of Statements

Every syllogism question is built from four basic statement types. Think of them as four soldiers: Universal Positive (A), Universal Negative (E), Particular Positive (I), and Particular Negative (O). The letters A-E-I-O come from Latin but just treat them as category labels. A says ALL, E says NO, I says SOME, O says SOME NOT. Your job is to combine two or more statements and check if the conclusion must be true.

• A-type: All S are P — strongest positive claim, applies to every member
• E-type: No S is P — strongest negative claim, total separation
• I-type: Some S are P — at least one, could be all, could be just one
• O-type: Some S are not P — at least one is excluded
• Remember: SOME means at least one, never zero
• Real-world truth does not matter — judge only by the statements given

Venn Diagram Method (Visual Approach)

Draw circles for each term and shade or tick to represent the statement. This is the safest method for 2-statement questions. All A are B means circle A sits fully inside circle B. No A is B means two separate circles with no overlap. Some A are B means two circles that overlap partially. Some A are not B means some part of circle A is outside circle B. Draw every possible valid diagram and check if the conclusion holds in ALL of them. If even one diagram breaks the conclusion, it does not follow.

• Draw ALL possible diagrams for the given statements, not just one
• A conclusion is valid only if it is true in every possible diagram
• All A are B — A is a subset of B (A inside B)
• No A is B — A and B are completely separate circles
• Some A are B — A and B have at least a small overlap
• Some A are not B — part of A is definitely outside B

Conclusion Rules (Quick Logic Table)

SSC CHSL often tests simple 2-statement syllogisms. These shortcut rules let you find the answer in under 30 seconds without drawing circles each time. The key pattern is: All + All gives All. All + No gives No. Some + All gives Some. Some + No gives Some-Not. Any combination involving an O-type statement almost always gives no definite conclusion. If both statements are particular (I or O type), no conclusion follows.

• All + All = All (e.g., All A are B, All B are C, so All A are C)
• All + No = No (e.g., All A are B, No B is C, so No A is C)
• Some + All = Some (e.g., Some A are B, All B are C, so Some A are C)
• Some + No = Some-Not (e.g., Some A are B, No B is C, so Some A are not C)
• I + I, O + O, I + O, O + I — no definite conclusion in most cases
• Reverse check: No A is B also means No B is A (E converts fully); Some A are B also means Some B are A (I converts fully)

Complementary Pairs and Either-Or Conclusions

SSC CHSL loves the Either-Or trap. When neither conclusion I nor conclusion II follows individually, check if they form a complementary pair. A complementary pair is: Some A are B (I-type) paired with No A is B (E-type), OR Some A are B paired with Some A are not B. If the two conclusions together cover all possibilities and are opposites, answer is Either I or II follows. This is a very common 1-mark gift in the exam.

• Either-Or applies only when neither conclusion follows on its own
• Complementary pairs: (I-type + E-type) or (I-type + O-type) for the same subject and predicate
• Both conclusions must talk about the same subject and predicate for Either-Or to apply
• If both conclusions follow independently, do not use Either-Or
• If only one follows, do not use Either-Or

Worked Example Walkthrough

This shows how to apply the rules step by step on a typical SSC CHSL-style question.

• Statements: All cats are dogs. Some dogs are birds.
• Conclusion I: Some cats are birds. Conclusion II: Some birds are cats.
• Step 1: All cats are dogs (A-type). Some dogs are birds (I-type).
• Step 2: Using rule — All + Some gives no standard conclusion (middle term dogs is NOT distributed in both).
• Step 3: Draw Venn diagram — cats inside dogs, dogs and birds overlap. Cats may or may not touch the birds region.
• Step 4: Neither conclusion I nor II necessarily follows. Check complementary pair — they are not complementary (same subject cats vs birds). Answer: Neither follows.
• Shortcut memory: All + Some does NOT guarantee a conclusion. Some + All does.

• Using real-world knowledge — the statement says All stones are living, you must accept it. Never reject a statement because it seems false in reality.
• Confusing Some + All with All + Some — order matters. Some A are B, All B are C gives Some A are C. But All A are B, Some B are C does NOT give Some A are C.
• Missing the Either-Or conclusion — aspirants mark Neither follows when the correct answer is Either I or II follows. Always check for complementary pairs when both conclusions seem wrong individually.
• Thinking SOME means only a few — in logic, Some means at least one, which includes the possibility of All. So if All A are B is given, it is also correct to say Some A are B.
• Forgetting conversion rules — No A is B can be flipped to No B is A. But All A are B cannot be flipped to All B are A. Only partial conversion works: All A are B flips to Some B are A.

• AEIO Army: A = All (strongest yes), E = No (strongest no), I = Some yes, O = Some no. Think A and E are Extreme, I and O are Only-partial.
• SANA Rule: Some + All = No solid conclusion going backward, but Some + All = Some going forward (Some A are B, All B are C = Some A are C). Remember: the ALL must come second.
• Flip Rule: E and I convert fully and freely (No A is B = No B is A; Some A are B = Some B are A). A converts only partially (All A are B = Some B are A, NOT All B are A). O does NOT convert at all.
• Either-Or Trigger: When BOTH conclusions fail alone AND they are a mirror pair (I + E or I + O on same subject-predicate), shout Either-Or and move on.

• SSC CHSL typically asks 2 to 3 syllogism questions per paper. They appear in sets of 1 question with 2 conclusions, or occasionally 3 conclusions. Expect 1 easy, 1 medium, rarely 1 tricky.
• The Either-Or type question appears in nearly every CHSL paper. If you learn only one advanced concept, learn this — it can be a guaranteed mark.
• Venn diagram method is safer for tricky questions; the logic table shortcut is faster for straightforward 2-statement questions. Practice both so you can switch based on time.
• Recent CHSL papers (2023-2024 tier) tend to use simple 2-statement formats with 2 conclusions. Three-statement syllogisms are rare but not impossible — solve them by chaining two at a time.
• Time target: each syllogism question should take no more than 45 to 60 seconds. If you are stuck beyond that, skip and return — do not let one question eat your Reasoning time.