Lecture � logic & language IIa

Prof Edgington - Merton St

@10 on Wednesday, 10 May, 2000

 

Kant?

contained in the definitions as plants contained in seeds

no end of new patterns you can put together � though the vast majority would be uninteresting

 

Predicates

see quantifying domains

Strawson (Introduction to Logical theory) � all John�s children are asleep does not have to be true, just because John has no true

but can always add in thereIsAn[isAChildOfJohn�s(x)]

Quantifiers (expressions for generality)

(Fs are G)

all/some/no

at most one, exactly one, most, many, few, 70%

Frege had no interest in these, since they play no rule in pure mathematical reasoning

Frege thought he could avoid restricted domains, because he wouldn�t need them

domains can be quantified as forAll[Person(x) �] within a predicate

David Wiggins wrote a paper about �most�

most[tigers have 3 legs] (false)

but most[not (tigers with three legs)] (true)

Single terms

includes: proper names, pronouns, demonstratives (this, that)

function: to pick out an object which a sentence says something about

 

Russell�s Theory of Descriptions

what about �The F is G� � is that part of Quantifiers or Single Terms?

1903/5 paper: Quantifiers

 

Law of excluded middle???

 

Frege

�On Sense and Meaning/Reference�

sense = mode of presentation of the object

�way of thinking� of the object

e.g. the �present king of France� does have a sense, it just doesn�t have an object to refer to

no object, no truth value (e.g. fictional characters like Odysseus) because Odysseus does not have a reference

�present king of france does not exist�: Frege agrees with Russell

but Russell did not like the idea of sense as a �mode of presentation of objects�