The square of opposition and the operations of conversion, observation, and contraption can be used to test
the validity of many deductive arguments having only one premise. For each of the following, assume that the
premise is true, then state whether the conclusion can be determined to be necessarily true using either the
square of opposition or one of the three operations. If it can, indicate which move on the square, or which
operation, preserves truth from the premise to the conclusion. If the argument is invalid, a true conclusion will
not guarantee a true premise. Be sure to indicate any such cases among the arguments.
No unripe apples taste good.
Therefore, it is false that all unripe apples taste good.
No mice are dangerous creatures.
Therefore, some dangerous creatures are mice.
Some professors are not fashionable dressers.
Therefore, no fashionable dressers are professors.
All driverless cars are safe vehicles.
Therefore, all unsafe vehicles are cars with drivers.
It’s false that some poets are ill-mannered dinner guests.
Therefore, some poets are not ill-mannered dinner guests.
It is false that some honor codes are codes that should occasionally be violated.
Therefore, it is false that some codes that should be occasionally violated are honor codes.
Some dogs are not pets that are permitted in the park.
Therefore, some pets not permitted in the park are not nondogs.
All individuals yearning for truth are searchers.
Therefore, all searchers are individuals yearning for truth.
It’s false that some snow leopards are creatures that don’t actually like snow.
Therefore, some creatures that don’t actually like snow are snow leopards.
No demonstrators are individuals treated gently by the authorities.
Therefore, all demonstrators are individuals treated roughly by the authorities
Sample Solution
