Directions for questions: In each of the following questions, two statements…
2025
Directions for questions: In each of the following questions, two statements are given, followed by two conclusions numbered I and II. You have to take the given two statements to be true even if they seem to be at variance from commonly known facts. Read the conclusions and then decide which of the given conclusions logically follows from the given statements, disregarding commonly known facts.
Statements:
All stars are bright. Sirius is bright.
Conclusions:
I. All stars are Sirius.
II. Sirius is a star.
- A.
Only conclusion I follows
- B.
Only conclusion II follows
- C.
Either conclusion I or II follows
- D.
Neither conclusion I nor II follows
Show answer & explanation
Correct answer: D
Concept: In a syllogism, a conclusion connecting the subject and predicate terms of two premises is valid only if the middle term (the term common to both premises) is distributed - that is, taken in its full extension - in at least one premise. If the middle term is undistributed in both premises, no definite relationship between the two end terms can be logically established.
Application: Here the middle term is "bright". In "All stars are bright" (a universal affirmative statement), the predicate "bright" is undistributed. In "Sirius is bright" (also affirmative), "bright" is undistributed again. Since "bright" is undistributed in both premises, no valid link can be drawn between "stars" and "Sirius".
Cross-check:
Concluding that all stars are Sirius would require every star to be identical to Sirius - the premises never state this; other bright things besides Sirius could exist.
Concluding that Sirius is a star would require every bright thing to be a star - the premises only say Sirius is bright, not that only stars are bright.
Since neither conclusion is logically forced by the premises, neither conclusion follows from the given statements.