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Syllogism Rules

Syllogisms are an essential part of logical reasoning, an aspect of thinking that permeates all aspects of our life, from basic decision-making to complex problem-solving. Understanding the rules of syllogism is important because these rules define valid logical deductions and enable clear, rational thinking.

Understanding the Rules of Syllogism

1. With two particular statements, no universal conclusion is possible

A particular statement refers to a statement that does not pertain to all members of a category but only to some. If all our premises are particular, we cannot draw a universal conclusion about every member of the category because our premises do not provide information about every member.

For Example:

Premise 1: Some dogs are friendly.

Premise 2: Some friendly creatures are mammals.

From these two particular statements, we can't draw a universal conclusion such as "All mammals are dogs." There's not enough information provided about all dogs or all mammals to make such a claim.

2. With two positive statements, no negative conclusion is possible

Positive premises assert something about a group or category. When you have two positive premises, it is illogical to come up with a negative conclusion, as this would contradict the premises.

For Example:

Premise 1: All apples are fruits.

Premise 2: All fruits are healthy.

From these positive premises, we can't draw a negative conclusion like "Some apples are not healthy." It contradicts the information given in the premises.

3. With two negative statements, no positive conclusion is possible

Negative statements deny something about a category or group. When two negative premises are given, it's illogical to derive a positive conclusion because such a conclusion contradicts the negative information provided.

For Example:

Premise 1: No cats are reptiles.

Premise 2: No reptiles can fly.

From these negative statements, we can't logically conclude a positive statement like "Some cats can fly." The conclusion contradicts the premises that have already denied certain qualities to cats and reptiles.

S.No. Statement Definite Conclusion Possible Conclusion
1. All A are B
  • All A are B
  • Some A are B .
  • Some B are A
  • All B are A
  • Some B are not A
2. Some A are B
  • Some A are B
  • Some B are A
  • All A are B
  • All B are A
  • Some A are not B
  • Some B are not A
3. Some A are not B Some A are not B
  • Some A are B
  • No A is B
  • No B is A
  • Some B are not A
  • All B are A
4. No A is B
  • No A is B
  • No B is A
No possibility is true
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FAQs

Why understanding syllogism rules is important in answering questions?

Understanding syllogism rules is important because it enhances logical thinking and reasoning abilities. It helps one to make valid deductions and arguments, which are crucial for addressing questions quickly and accurately in exams.

How many rules are there in syllogism?

Classical Aristotelian syllogisms have a set of 6 rules for determining the validity of syllogistic forms. These include rules such as: every syllogism must have three and only three terms, the middle term must be distributed in at least one premise, among others.

How is a syllogism structured?

A syllogism is typically structured in three parts: two premises and a conclusion. The first premise is a general statement, the second premise is specific, and the conclusion is a logical deduction from the premises.

For Example:

"All mammals are warm-blooded (general statement). Dogs are mammals (specific statement)."

Therefore, dogs are warm-blooded (conclusion).

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