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Syllogism Notes

Questions

3 questions per paper

Difficulty

Medium

Importance

High yield for SSC and Banking sector exams

Overview

Syllogism is a logical reasoning topic based on deducing conclusions from given statements using Venn diagrams or logical rules. It is a high-scoring pillar in SSC and Banking exams, testing an aspirant's ability to identify truth based strictly on the provided premises rather than real-world facts.

Basic Categorical Propositions

Understanding the four standard types of statements (All, Some, No, Some Not) is essential for drawing accurate Venn diagrams. These represent the logical relationships between subject and predicate terms.

  • All A are B: A is a subset of B
  • Some A are B: Overlapping regions between A and B
  • No A are B: Disjoint sets with no intersection
  • Some A are not B: Part of A is restricted from B

The Concept of Possibility

A possibility is true only if it does not violate the basic structure of the statements provided. If a conclusion is already definite, it is usually not considered a 'possibility' in competitive exams.

  • Possibility is true if no statement is contradicted
  • Can be true refers to 'at least one diagram is possible'
  • If a relationship is definite, possibility is redundant
  • Check for possibility by expanding the Venn diagram without breaking rules

Either-Or Conditions

An 'Either-Or' case occurs when both conclusions are false individually but together cover the entire scope of the relationship. This is a common trap requiring precise checklist validation.

  • Both conclusions must be individually false
  • Subject and predicate must be identical
  • One must be positive and one must be negative
  • Valid pairs: All + Some Not, Some + No

Formula Sheet

If + If = Negative conclusion

All + All = All

All + No = No

Some + Some = No conclusion

Exam Tip

Always draw all possible scenarios, especially for 'Some' and 'Possibility' questions, to avoid falling for partially correct conclusions.

Common Mistakes

  • Applying personal real-world knowledge instead of sticking strictly to the given statements.
  • Assuming that if a conclusion is possible, it is automatically true.
  • Failing to check all possible Venn diagram variations, leading to missing a counter-example.

More Revision Notes

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