In a valid standard form of categorical syllogism, if predicate term is distributed in the conclusion, then it must be distributed

The correct answer is C. In a standard form syllogism, the predicate of the conclusion is the major term, and the premise that contains the major term is the major premise. The rule is that a term distributed in the conclusion must also be distributed in the premise where it appears. So if the major term is distributed in the conclusion, it must be distributed in the major premise. Violating this gives the fallacy of illicit major.

Take the example: No P is M; All S is M; therefore No S is P. The predicate P is distributed in the conclusion, an E proposition distributes both terms. It is also distributed in the major premise, 'No P is M', which is why the argument is valid.

• A (both premises): Not required. The minor premise may or may not distribute the major term. In the example above, 'All S is M' does not distribute P, and the syllogism is still valid.
• B (minor premise): The minor premise is the one containing the minor term, not the major term. It has no bearing on the major term's distribution.
• D (none): Wrong, because the major premise must distribute the term.

The concept is the distribution of terms and the rules of validity, which are the core of Venn-diagram and syllogism questions in the Reasoning section of CSAT. Mains ethics answers that involve structured reasoning also benefit from this discipline.

Trap: Aspirants identify the major premise by its position (the first or second line), when it is defined by its content: the premise containing the predicate of the conclusion.