Week T wo
- Syllogism --> Premise 1, Premise 2, then Conclusion
- All men are mortal (P1)
- Socrates is a man (P2)
- Therefore Socrates is mortal (Conclusion)
-- Truth preserving or deductively validruth of the
premises leads to the validity of the conclusion
-- Deductively invalid argument:
- (P1) If I go to the store then I will have cigarettes
- (P2) I have cigarettes
- (C) I went to the store
- if you find the conclusion to be false then the argument is
deductively invalid. (P1) Nancy is taller than Scott
(P2) Scott is taller than Mohammed
(C) Nancy is taller than Mohammed
---> Aristotelian logic is limited to categories but not
relations such as these.
--> you need a new logic to account for this type of
The New Logic:
- Frege: Predicate logic (second order predicate logic)
- Russell & Whitehead --> definitive and used in
- numbers are logical objects where you find in sets
- Logisism: logical development in order to figure how
mathematics works (which is a form of logic)
"Pegasus is a winged-horse"
-- pegasus does not exist
- Plato's Beard: every word in every sentence has to refer
2 to something if that sentence is meaningful
- Pegasus subsists and does not exist (not spacio-
Russell's Old Theory of Denoting
The denoting concept pulls the thing being denoted into the
Problematic if you want to talk about denoting objects as
they are (absent)
Sense of a proper name = sense
Sense of a sentence = thought
- we can associate different senses for a proper name.
- a sense is a descriptive phrase
- NAPOLEON (linguistic item)
subjective conceptions (how you connect linguistics to
3 --Referent: Napoleon (spacio temporal object)
--Meaning: sense and reference
--> Sense: not a mental object, objective, public whereas
ideas/mental objects are subjective, particular and private.
Senses can be universally grasped whereas ideas cannot.
---> Sense of a sentence (thought) - has truth value
---> Ideas do not have truth value? Sentences without
---> Ideas are subjective so cannot be true or false
because they are private.
- True propositions (thoughts)
- does not care about how people make inferences
- they only care about the logic behind the inferences.