Syllogisms - Reasoning for SSC

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What are Syllogisms?

Syllogism = Logical reasoning from two statements (premises) to reach a conclusion.

Format

Statements:

  1. All A are B
  2. All B are C

Conclusions: I. All A are C → Follows II. Some C are A → Follows

Types of Statements

  1. Universal Positive (A): All A are B
  2. Universal Negative (E): No A is B
  3. Particular Positive (I): Some A are B
  4. Particular Negative (O): Some A are not B

Venn Diagram Method

Best method for SSC exams!

Rule 1: All A are B

[Venn: Circle A completely inside Circle B]

Rule 2: No A is B

[Venn: Circles A and B separate, no overlap]

Rule 3: Some A are B

[Venn: Circles A and B overlapping]

Important Rules

  1. All + All = All
  2. No + All = No
  3. Some + All = Some
  4. No + No = No conclusion
  5. Some + Some = No conclusion

Complementary Pairs

  • All A are BSome A are not B (Complementary)
  • No A is BSome A are B (Complementary)

Note: At least one from complementary pair always follows!