या तो-या तथा विशेष स्थितियाँ
Either-Or and Special Cases
Either-or is the trickiest pattern in syllogism, and SBI Clerk plants it precisely because so many candidates miss it. It appears when two conclusions each fail on their own, yet together they cover every possibility, so one of them must be true. Learning the one rule that produces an either-or answer, plus a few special conversion cases, closes the last gap between three marks and a full five in this set.
The Complementary Pair Rule
An either-or answer arises only when two conclusions form a complementary pair and both are individually false. A complementary pair has the same subject and predicate but opposite type in a specific way: 'Some A are B' pairs with 'Some A are not B', and 'All A are B' pairs with 'No A are B'. If neither conclusion follows alone, but the two exhaust every case between them, mark 'either follows'. This is the only situation that yields an either-or answer, so check for it whenever two single conclusions both fail.
| Conclusion 1 | Conclusion 2 | Complementary? |
|---|---|---|
| Some A are B | Some A are not B | Yes → either-or possible |
| All A are B | No A are B | Yes → either-or possible |
| Some A are B | All A are B | No — not a valid pair |
| No A are B | Some A are not B | No — both can be true together |
How to Confirm an Either-Or
Run a two-step check. First, verify neither conclusion follows definitely on its own — if either one does, the answer is simply that conclusion, not either-or. Second, confirm the two conclusions share the same subject and predicate and sit in a genuine complementary pair. Only when both steps pass do you mark 'either A or B follows'. Skipping the first step is the classic error, because an either-or can never be correct if one of the two conclusions already holds by itself.
Either-or valid ⟺ (Conclusion 1 false alone) AND (Conclusion 2 false alone) AND (they are a complementary pair)
Special Case: No and Some-not
A 'No A are B' statement quietly gives you extra conclusions. Besides converting to 'No B are A', it also yields 'Some A are not B' and 'Some B are not A', because if the groups are fully separate then some of each certainly lies outside the other. Recognising these hidden outputs of a 'No' statement often supplies the exact conclusion the exam is testing, and it explains why a 'No' is one of the most information-rich statements you can be given.
Solved Examples
Example: 'Some Morks are Zephyrs' gives two conclusions: 'Some Morks are Table' and 'Some Morks are not Table'. Neither follows alone, but together they cover every case, so the answer is either one or the other follows — the complementary pair rule in action.
✗ Marking either-or when one conclusion already follows on its own | ✓ Confirming both fail alone before choosing either-or
Reading the Options Carefully
Either-or questions are lost as often on careless option-reading as on the logic itself. The exam may list 'either 1 or 2 follows' as one option and 'both 1 and 2 follow' as another, and a hurried candidate ticks the wrong one. Remember that either-or is not the same as both: either-or means exactly one of the pair is true in any given drawing, while both would mean the two hold together, which a complementary pair can never do. Slow down for two seconds on the option list whenever you sense a complementary pair, match your conclusion to the precise wording, and you will bank a mark that the rest of the room routinely forfeits by confusing 'either-or' with 'both' or by missing the pair entirely.
Either-or तभी जब दोनों निष्कर्ष अलग-अलग असत्य हों और वे पूरक जोड़ी बनाएँ (Some/Some-not या All/No)। 'No' कथन 'Some-not' निष्कर्ष भी देता है।
Exam Pointer — SBI Clerk plants at least one either-or in most syllogism sets, and it is the single most-missed pattern. The trigger is two conclusions that both fail alone but form a complementary pair. Confirm both fail first, then match the exact option wording — never confuse 'either-or' with 'both follow'. This one check often decides your syllogism score.
60-Second Recap
- Either-or needs a complementary pair with both parts false alone.
- Valid pairs: Some/Some-not and All/No, same subject and predicate.
- A 'No' statement also yields 'Some-not' conclusions both ways.
- Either-or means exactly one is true — never the same as 'both'.