Phil 140 - Module 4

Proposition

a sentence that is used to make a claim about how things are, true or false

Terms - Subject and Predicate

terms : a word or phrase that can serve as the subject of a proposition

subject : denotes the class whose members are claimed to be included in or excluded from a class of things by the categorial proposition 

predicate : denotes the class of things that members of the subject class are claimed to be included in or excluded from 

• example : Some dogs are not good pets 

  • Subject - dogs

  • Predicate - good pets 

4 Standard Forms of S and P

A - All S are P  -  universal positive 

E - No S are P  -  universal negative 

I - Some S are P  -  particular positive 

O - Some S are not P  -  particular negative 

Quantifier 

an expression which specifies how many members of the subject class are included in or excluded from the predicate class

all, no, some 

Copula

an expression which links the subject term with the predicate term

are, are not

Quantity and Quality of Categorial Propositions

Quality : a matter of whether a proposition affirms or denies class membership

• positive - members are included

• negative - members are excluded

Quantity : how many members off the class are addressed

• universal - make a claim about every member of the subject class; All, No

• particular - make claims about one or more, but not all members; Some

How to transform statements into categorial form 

1. transform the subject and predicate terms into a class, make it a plural noun

• all professors are evil - all professors are evil people

2. copulas - change it so are or are not are present in the statement

3. quantifiers - have to make the decision if its universal or particular; have to add all, no, or some

4. if its an individual subject - say all things identical to

Transformations of Categorial Propositions  - 3 

a) switch the subject and predicate terms 

b) change the quality of proposition 

• A - “All S are P” becomes “No S are P”

o   E - “No S are P” becomes “All S are P”

o   I - “Some S are P” becomes “Some S are not P”

o   O - “Some S are not P” becomes “Some S are P”

c) replace one or more terms with their complements 

Complements

an expression which denotes the class whose members consist of everything that falls outside the class denoted by the original term

initial - iguanas

complement - non-iguanas, things that are not iguanas

Three Operations - Transformations

1. Conversion - a) transformation only - switch S and P

2. Obversion - b) and c) transformation - predicate complement, only time you change the quantifier and copula

3. Contraposition - a) and c) transformation - subject and predicate complement

Equivalence of Transformations 

Obverse - always equivalent 

Converse - not equivalent with A and O

Contrapositive - not equivalent with E and I