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PHIL112
week six
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Eloise
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Cards (12)
Quantified logic
subject - what statement is about
predicate - thing said about subject
quantifier expressions
Multiple place predicates (multiple subjects)
one place: "... is blue"
two place: "...is taller than..."
three place: "...likes...more than..."
four place: "...bought...from....for...."
etc.
Quantifier expressions
indicates how many things/how much stuff
numerically definite: 2/100/four
numerically indefinite: some/all
Generalisation
An ambiguous generalisation contains one or more quantifier expressions
Can be universal or existential
Universal generalisation
"All" / "every"
Existential generalisation
"Some" / "there are"
Conversion (reasoning with generalisation)
switching roles of subject and predicate
'All cats are felines' - 'All felines are cats'
'Every car is not a bike' - 'Every bike is not a car'
Complementation of terms
I. Adding 'non' to front of term
II. Taking away 'non'
Swans = non-swans
Contrapositive
I. convert generalisation; and
II. complement all terms
conversion - 'all mammals are cats'
complement - 'all non-mammals are non-cats'
Obversion
I. Turn generalisation from an affirmative to a negative, or vice versa
II. Complement the predicate term
'some cats are fluffy'
'some cats are not fluffy'
'some cats are not non-fluffy'
Obversion form
All Fs are Gs - All Fs are not non-Gs
Syllogisms
I. 2 generalisations as the premises
II. a generalisation as the conclusion
III. 3 distinct class terms - 1/3 appear in both premises = 'middle term'