Syllogisms – Civil Service Exam – Civil Service Exam Help

Syllogisms - Civil Service Exam

Introduction to Syllogisms

A syllogism is a form of deductive reasoning where a conclusion is drawn from two or more given premises that are assumed to be true. A classic syllogism involves three parts:

Major Premise: A general statement or assumption.
Minor Premise: A specific statement that relates to the major premise.
Conclusion: A deduction made on the basis of the premises.

Structure of a Syllogism

Syllogisms typically involve three terms:

Major Term: The predicate of the conclusion.
Minor Term: The subject of the conclusion.
Middle Term: The term that appears in both premises but not in the conclusion.

Types of Syllogisms

Categorical Syllogisms: Deal with sets and their relationships to one another.
Conditional Syllogisms: Use if-then structures.
Disjunctive Syllogisms: Use either-or scenarios.

Rules for Valid Syllogisms

To determine if a syllogism is valid, it must satisfy the following:

All three statements must be categorical propositions.
The middle term must be distributed at least once.
If a term is distributed in the conclusion, it must be distributed in a premise.
The premises must not both be negative; if one premise is negative, the conclusion must be negative.

Common Fallacies in Syllogisms

Undistributed Middle: The middle term does not cover all its possible cases.
Illicit Major or Minor: A term is distributed in the conclusion but not in the premises.
Exclusive Premises: Both premises are negative.
Existential Fallacy: Concluding particular existence from universal premises.

Examples of Syllogisms

Example 1

Major Premise: All mammals are warm-blooded.
Minor Premise: All whales are mammals.
Conclusion: All whales are warm-blooded.
Analysis: Valid, as the conclusion follows logically from the premises.

Example 2

Major Premise: Some athletes are football players.
Minor Premise: Some football players are tall.
Conclusion: Some athletes are tall.
Analysis: Invalid, this commits the fallacy of undistributed middle as the connection between athletes and being tall is not logically established.

How to Approach Syllogisms in Tests

Identify and label the premises and conclusion.
Determine the three terms and their roles in the syllogism.
Check for logical connections and the distribution of terms.
Identify any potential fallacies.
Assess the validity of the conclusion based on the premises.

Practice Test in Syllogism - Civil Service Exam

Question 1

Category: Analytical Ability
Subcategory: Syllogism
Difficulty: 2
Question:
Statements:

All metals are conductive.
Some conductive materials are not metals.
No metal is transparent. Conclusions: I. Some conductive materials are transparent. II. No transparent material is conductive. III. Some transparent materials are not conductive.

Choice A: Only conclusion III follows
Choice B: Only conclusions I and III follow
Choice C: Only conclusions II and III follow
Choice D: Neither conclusion I, II, nor III follows
Answer: A
Solution:
Conclusion I is not supported directly by any statement and contradicts the general exclusivity of metals and transparency. Conclusion II incorrectly assumes a reverse condition that is not supported by the statements. Conclusion III is correct, as some conductive materials are not metals, and if metals are the only non-transparent conductive materials, then it follows that some transparent materials are not conductive.

Question 2

Category: Analytical Ability
Subcategory: Syllogism
Difficulty: 2
Question:
Statements:

All journalists are observant.
Some observant individuals are introverts.
All introverts enjoy solitude. Conclusions: I. Some journalists are introverts. II. Some introverts are journalists. III. Some journalists enjoy solitude.

Choice A: Only conclusion III follows
Choice B: Only conclusions I and II follow
Choice C: Only conclusions II and III follow
Choice D: All conclusions follow
Answer: A
Solution:
Conclusion I is possible but not necessarily true, as not all observant individuals are introverts. Conclusion II assumes that journalists being introverts is established, which it is not. Conclusion III logically follows since some observant individuals (including potentially some journalists) are introverts, and all introverts enjoy solitude.

Question 3

Category: Analytical Ability
Subcategory: Syllogism
Difficulty: 2
Question:
Statements:

All flowers are beautiful.
All beautiful things attract attention.
Some things that attract attention are dangerous. Conclusions: I. Some flowers are dangerous. II. All flowers attract attention. III. Some dangerous things are beautiful.

Choice A: Only conclusion II follows
Choice B: Only conclusions II and III follow
Choice C: Only conclusions I and II follow
Choice D: All conclusions follow
Answer: B
Solution:
Conclusion I is not directly supported by the statements, as the dangerous aspect does not necessarily overlap with flowers. Conclusion II is correct because all beautiful things, including all flowers, attract attention. Conclusion III logically follows since some things that attract attention (which include some beautiful things) are dangerous.