Logic6

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Author:
faulkebr
ID:
112393
Filename:
Logic6
Updated:
2011-10-26 17:43:26
Tags:
Square opposition
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Description:
6.5
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  1. Subcontraries
    • I and O
    • If one is False, the other must be True
    • CANT both be false
  2. Superalternation
    • A has corresponding I
    • Ehas corresponding O
    • The superaltern implies the TRUTH of its corresponding subaltern
  3. Contradictories
    • Cant both be True
    • Cant both be False
    • A - O
    • E - I
  4. Contraries
    • Cant both be True
    • If one is true, the other must be False
    • But if one is False, then we can infer nothing about the other
  5. Conversion
    • Replace the subject and Predicate (just switch)
    • Only works for E and I statements
    • No S are P = No P are S
    • O and A statements cant work (except by lim.)
  6. Convert by Limitation
    • Turn A statements into I statements
    • All Sare P = Some P are S
    • Still just switch the S and P
    • Only works for A statemets
    • One way inference
  7. Subcontraries
    • I, O
    • Cant both be False
    • Can both be True
  8. Sub alternation
    • If one is true you can immediately infer the other is True
    • A -> I
    • E -> O
    • If A or E is False, then their corresponding subalterns are undetermined
  9. Obversion
    • Used in all statements
    • Change quality of proposition (affirmative/Negative)
    • Replace predicate term with its complement
    • A: all s are p - E: No S are non p
    • E: No s are p - A: all s are non p
    • I: some s are p - O: some s ar notnonp
    • O: Some s is not p-I:some s is non p
  10. Contraposition
    • replace the subject term with the complement of the predicate term
    • Replace the predicate term with the complement of its subject term
    • Not all contrapositives are valid
  11. Contrapositive by lim.
    • works only for E statements
    • E -> O

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