Logical Deduction - Section 4
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In each of the following questions, three statements are given followed by four conclusions numbered I, II, III and TV. You have to take the given statements to be true even if they seem to be at variance with commonly known facts and then decide which of the given conclusions logically follows from the given statements disregarding commonly known facts.
| 1. | Statements: Some dogs are rats. All rats are trees. Some trees are not dogs. Conclusions: Some trees are dogs. All dogs are trees. All rats are dogs. No tree is dog. |
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Answer: Option B Explanation: Some dogs are rats. All rats are trees. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some dogs are trees'. I is the converse of this conclusion and so it holds. All rats are trees. Some trees are not dogs. Since the middle term 'trees' is not distributed even once in the premises, no definite conclusion follows. |
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Answer: Option D Explanation: All benches are desks. Some desks are roads. Since the middle term 'desks' is not distributed even once in the premises, no definite conclusion follows. Some desks are roads. All roads are pillars. Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some desks are pillars'. II is the converse of this conclusion and so it holds. All benches are desks. Some desks are pillars. Since the middle term 'desks' is not distributed even once in the premises, no definite conclusion follows. However, I and IV involve the extreme terms and form a complementary pair. So, either I or IV follows. |