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Traditional Logic- Rules
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Terms in this set (29)
Rule of Contradiction
Contradictory statements are statements that differ in both quality and quantity
Rule of Contraries
Two statements are contrary to one another if they are both universals but differ in quality
Rule of Subcontraries
Two statements are subcontrary if they are both particular statements that differ in quality
Rule of Subalterns
Two statements are subalternate if they have the same quality but differ in quantity
1st Rule of Opposition
Contradictories cannot at the same time be true nor at the same time be false
2nd Rule of Opposition
Contraries cannot at the same time both be true, but can at the same time both be false
3rd Rule of Oppostion
Subcontraries may at the same time both be true, but cannot at the same time both be false
4th Rule of Opposition
Subalterns may both be true or both be false
Rule of Double Negation
A term which is not negated is equivalent to a term that is negated twice
Essential Law of Argumentation
If the antecedent is true, the consequent must also be true
Principle of Reciprocal Identity
Two terms that are identical with a third term are identical to each other
Principle of Reciprocal Non-Identity
Two terms, one of which is identical with a third term and the other of which is nonidentical with that third term, are nonidentical to each other
Dictum de Omni
What is affirmative universally of a certain term is affirmed of every term that comes under that term
Dictum de Nullo
What is denied universally of a certain term is denied of every term that comes under that term
Rule I
There must be three and only three terms
Rule II
The middle term must not occur in the conclusion
Rule III
If a term is distributed in the conclusion, then it must be distributed in the premises
Rule IV
The middle term must be distributed at least once
Rule V
No conclusion can follow from two negative premises
Rule VI
If the two premises are affirmative, the conclusion must also be affirmative
Rule VII
If either premise is negative, the conclusion must be negative
Fallacy of Four Terms
There are four clearly distinguishable terms in a syllogism
Fallacy of Equivocation
One of three terms is used in argument in two different senses
Fallacy of Illicit Major
The major term is distributed in the conclusion but not in the major premise
Fallacy of Illicit Minor
The minor term is distributed in the conclusion but not in the minor premise
Fallacy of Undistributed Middle
The middle term is not distributed in either premise
Fallacy of Exclusive Premises
When rule V is violated
Fallacy of Drawing a Negative Conclusion from Affirmative Premises
when rule VI is violated
Fallacy of Drawing an Affirmative Conclusion from Negative Premises
when rule VII is violated
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