Question Details

Which one of the following formal fallacies is committed in the given argument?
All snakes are reptiles.
Some snakes are poisonous creatures.
Therefore all poisonous creatures are reptiles.

Options

Fallacy of Illicit process of major term

Fallacy of Illicit process of minor term

Fallacy of undistributed middle term

Fallacy of four terms

Show Answer

Correct Answer :

Option B

Fallacy of Illicit process of minor term

Solution :

The correct option is Fallacy of Illicit process of minor term (often simply called Illicit Minor).

To understand why this argument commits the fallacy of the illicit minor, let us analyze the structure of the categorical syllogism step-by-step:
1. Identify the terms:
- Major Term (P): The predicate of the conclusion, which is "reptiles".
- Minor Term (S): The subject of the conclusion, which is "poisonous creatures".
- Middle Term (M): The term appearing in both premises but not in the conclusion, which is "snakes".

2. Analyze the distribution of terms in the premises:
- Major Premise: "All snakes (M) are reptiles (P)." This is an A-proposition (All M are P). In an A-proposition, the subject term (snakes) is distributed, but the predicate term (reptiles) is undistributed.
- Minor Premise: "Some snakes (M) are poisonous creatures (S)." This is an I-proposition (Some M are S). In an I-proposition, neither the subject (snakes) nor the predicate (poisonous creatures) is distributed. Therefore, the minor term "poisonous creatures" is undistributed in the minor premise.

3. Analyze the distribution of terms in the conclusion:
- Conclusion: "Therefore all poisonous creatures (S) are reptiles (P)." This is an A-proposition (All S are P). In an A-proposition, the subject term (S) is distributed. Thus, the minor term "poisonous creatures" is distributed in the conclusion.

4. Apply the rules of syllogism:
- A formal rule of a valid categorical syllogism states that any term distributed in the conclusion must also be distributed in the premise where it occurs.
- Here, the minor term "poisonous creatures" is distributed in the conclusion but was undistributed in the minor premise.
- Violating this rule by distributing the minor term in the conclusion without distributing it in its premise commits the Fallacy of Illicit process of minor term.