What is asked
Two to four statements with two conclusions (Prelims) or a "which conclusion follows" format with three to four statements (Mains). Since 2020 nearly every paper uses "only a few" and possibility conclusions. Options: Only I, Only II, Either I or II, Neither, Both.
Rules table
| Statement | Definitely true | Definitely false |
|---|---|---|
| All A are B | Some A are B; Some B are A | No A is B; Some A are not B |
| Some A are B | Some B are A | No A is B |
| No A is B | No B is A; Some A are not B | Some A are B; All A are B |
| Some A are not B | - | All A are B |
| Only a few A are B | Some A are B AND Some A are not B | All A are B; No A is B |
Chaining (two statements)
- All + All = All (All A are B, All B are C gives All A are C).
- All + No = No; Some + All = Some; Some + No = Some-not (Some A are not C).
- No + All, Some + Some, No + Some, All + Some give no definite conclusion between the end terms.
Possibility conclusions
"All A being B is a possibility" follows if you can draw a Venn diagram where it is true without breaking any statement. It fails when a statement already rules it out - e.g. "Only a few A are B" makes "All A being B" impossible, and "No A is B" makes any A-B overlap impossible. If there is no definite relation between two terms, all their possibilities generally follow.
Either-or rule
Choose "Either I or II" only when (1) neither conclusion is definite, (2) both are about the same two terms, and (3) together they cover all cases: Some + No (Some A are B / No A is B) or All + Some-not (All A are B / Some A are not B).
Worked example
Statements: Only a few books are copies. No copy is a file. Conclusions: I. Some books are files. II. No book is a file. The books that are copies are not files; the other books may or may not be files, so neither conclusion is definite. They are a Some/No pair on books and files, so the answer is Either I or II.
Traps
- "Some A are not B" does not mean "Some B are not A".
- From "Only a few A are B", the conclusion "Some A are not B" is definitely true.
- Do not use real-world knowledge - treat statements as true even if they sound odd.
Time target
45-60 seconds per question in Prelims; up to 75 seconds for Mains four-statement versions.