Logical Reasoning - Logical Deduction - Discussion
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.
Statements: Some bricks are trees. All trees are pens. All pens are boats.
Conclusions:
- Some boats are bricks.
- Some pens are bricks.
- Some trees are bricks.
- Some bricks are boats.
III is the converse of the first premise and so it holds.
Some bricks are trees. All trees are pens.
Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some bricks are pens'. II is the converse of this conclusion and so it holds.
All trees are pens. All pens are boats.
Since both the premises are universal and affirmative, the conclusion must be universal affirmative and should not contain the middle term. So, it follows that 'All trees are boats'.
Some bricks are trees. All trees are boats.
Since one premise is particular, the conclusion must be particular and should not contain the middle term. So, it follows that 'Some bricks are boats'. Thus, IV follows. I is the converse of this conclusion and so it also holds.
And this conclusion "all trees are boats" is compared with premise "some brics are trees" and then conclusion are "some brics are boats" and "some boats are bricks".
Hence option I and 4th also follows.