Deductive Logic Part 56

(2) All the men who do not row play cricket.

(3) All impeccable beings are other than human,

(4) Some prejudiced persons are not dishonest.

3. Prove indirectly the truth of the contrapositive of 'All A is B.'

4. Criticise the following as immediate inferences--

(1) All wise men are modest.

.'. No immodest men are wise.

(2) Some German students are not industrious.

.'. Some industrious students are not Germans.

(3) Absolute difference excludes all likeness.

.'. Any likeness is a proof of sameness.

(4) None but the brave deserve the fair.

.'. All brave men deserve the fair.

(5) All discontented men are unhappy.

.'. No contented men are unhappy.

(6) Books being a source of instruction, our knowledge must come from our libraries.

(7) All Jews are Semitic.

.'. Some non-Semitic people are not Jews.

5. Show by what kind of inference each of the subjoined propositions follows from

All discontented men are unhappy.

(1) All happy men are contented.

(2) Some discontented men are unhappy.

(3) Some contented men are happy.

(4) Some unhappy men are not contented.

(5) No discontented men are happy.

(6) Some happy men are contented.

(7) Some contented men are not unhappy.

(8) Some unhappy men are discontented.

(9) No happy men are discontented.

(10) Some discontented men are not happy.

(11) Some happy men are not discontented.

(12) None but unhappy men are discontented.

From how many of these propositions can the original one be derived?

And why not from all?

CHAPTER VII.

What kind of inference have we here?--

(1) None but the ignorant despise knowledge.

.'. No wise man despises knowledge.

(2) A is superior to B.

.'. B is inferior to A.

CHAPTER VIII.

Fill up the following enthymemes, mentioning to which order they belong, and state which of them are expressed in problematic form--

(1) I am fond of music: for I always like a comic song.

(2) All men are born to suffering, and therefore you must expect your share.

(3) Job must have committed some secret sins: for he fell into dreadful misfortunes.

(4) Latin was the language of the Vestals, and therefore no lady need be ashamed of speaking it.

(5) None but physicians came to the meeting. There were therefore no nurses there.

(6) The human soul extends through the whole body, for it is found in every member.

(7) No traitor can be trusted, and you are a traitor.

(8) Whatever has no parts does not perish by the dissolution of its parts. Therefore the soul of man is imperishable.

Is the suppressed premiss in any case disputable on material grounds?

CHAPTERS IX-XVIII.

Refer the following arguments to their proper mood and figure, or show what rules of syllogism they violate.