mediate inference/syllogisms

MEDIATE INTERFERENCE/SYLLOGIS

MS

SYLLOGISMAristotle define syllogism as a "prepositional expression in which for certain things which have been laid down (premises), something other than what has been laid down follows of necessity from being so (conclusion).

CATEGORICAL SYLLOGISM

Is a syllogism in which the propositions are all categorical. It is complex logical unit made up of terms and propositions.

STRUCTURAL ELEMENTS OF CATEGORICAL SYLLOGISM

BASIC PROPOSITION IN A CATEGORICAL SYLLOGISM

1. Major Premise - the premise which contains the major term. Generally, this premise has greater extension than other propositions of the syllogism.2. Minor Syllogism - the premise which contains the minor term. Usually, this is the second proposition and is preceded by the conjunction but.3. Conclusion - the last proposition which has been necessarily derived from the premises. 

BASIC TERMS IN A CATEGORICAL SYLLOGISM

1. Major Term - it is the predicate of the conclusion and is found in the major premise. It is usually designated by "P" which means the predicate of the conclusion.2. Minor Term - it is the subject of the conclusion and is found in the minor premise. It is usually designated by "S" which the subject if the conclusion.3. Middle Term – occurs in each of the premises but not in the conclusion.

Examples:

Every BPSC student is a human being ---------- Major Premise

Mylene is a BPSC student ---------- Minor Premise

Therefore, Mylene is a human being --------- Conclusion

To indicate the different elements of the categorical syllogism, the following figures are used:The major term ----------The minor term ----------

The middle term ---------

To illustrate it:

All monkeys are animals MP (major premise)But all chimps are monkeys mp (minor premise)Therefore, all chimps are animals C (conclusion)

RULES GOVERNING THE VALIDITY OF CATEGORICAL SYLLOGISM

RULES OF TERMSRule No. 1.

There must only be three terms. No more, no less.

Example:

All BCCnians are students.But Jason is a student.Therefore, Jason is a BCCnians.

FALLACIES COMMITTED ON THIS RULE

FALLACY OF FOUR TERMS OR FIVE TERMSIt is committed when there are more than three terms which are evident in the syllogism.

Example:

Every man is a sinner.But Pope John Paul is a man.Therefore, the parish priest is a sinner.

FALLACY OF EQUIVOCATIONIt is committed when the term applied to one proposition has a different meaning as applied to the other proposition in the syllogism.

Example:

Every pen is an instrument for writing.But a pen is an enclosure for pigs.Therefore, every enclosure for pigs is an instrument for writing.

FALLACY OF AMPHIBOLYIt is omitted when there is the use of analogous terms.

Example:

God is love.But love is blind.Therefore, God is blind.

Rule No. 2.The major term cannot become universal in the conclusion unless it is universal in the premise.

Example:

Every plant is a living thing.Stones are not living things.Therefore, stones are not plants.

FALLACY OF ILLICIT MAJOR

Example:

All cats are mammals. – particularBut no dogs are cats.Therefore, no dogs are mammals. – universal

FALLACY COMMITTED ON THIS RULE

Rule No. 3.The minor term cannot become universal in the conclusion unless it is universal in the premise.

Example:

All singers are musicians.But every musician is an artist.Therefore, all singers are artists.

FALLACY OF ILLICIT MINOR

Example:

Every circle is round.But every circle is a figure.Therefore, every figure is round.

FALLACY COMMITTED ON THIS RULE

Rule No. 4The middle term must not appear in the conclusion.

FALLACY COMMITTED ON THIS RULE

FALLACY OF ILLICIT MIDDLE TERM

Example:

All cats are animals.But no dogs are cats.Therefore, no cats are mammals.

Rule No. 5The middle term must be universal at least once.

FALLACY COMMITTED ON THIS RULE

FALLACY OF UNDISTRIBUTED MIDDLE TERM

Example:

The earth is a planet.But the Mars is a planet.Therefore, the Earth is Mars.

Rule No. 6If both premises are affirmative, the conclusion must also be affirmative.

FALLACY COMMITTED ON THIS RULE FALLACY ON NEGATIVE CONCLUSION

Example:

Labanos is not a fruit.But all fruits are delicious.Therefore, labanos is not delicious.

RULES ON THE QUALITY OF PROPOSITIONS

Rule No. 7If one premise is affirmative and the other premise is negative, the conclusion is negative.

FALLACY COMMITTED ON THIS RULE

FALLACY OF AFFIRMATIVE CONCLUSION

Example:

All Americans are not Asians.But all Filipinos are Asians.Therefore, all Filipinos are not Americans.

Rule No. 8If both premises are negative, no conclusion follows.

FALLACY COMMITTED ON THIS RULE FALLACY ON NEGATIVE PREMISES

Example:

Some insects are not flies.But some insects are not grasshoppers.Therefore, some grasshoppers are not flies.

Rule No. 9At least one of the premises must be universal. If both premises are particular, then no conclusion follows.

FALLACY COMMITTED ON THIS RULE FALLACY OF UNIVERSAL CONCLUSION

Example:

Some insects are not grasshoppers.But, all insects are small.Therefore, all grasshoppers are small.

RULES ON THE QUANTITY OF PROPOSITIONS

END OF PRESENTATION

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