- #1
Bacle
- 662
- 1
Does anyone know/understand the different definitions for Inconsistency
in Sentence Logic and in Predicate Logic?
I know in Sentence Logic, that a sentence ( a Wff, actually) S is
contradictory, if from S we can derive (using theorems of
truth-functional logic ) a sentence of the type A&~A , where '&'
is 'and' and '~' stands for negation, i.e., we assume S, and, using
theorems, we can conclude, using MP, that S->(A&~A).
How do we define contradiction in Predicate Logic, tho? Is it
defined both syntactically and semantically, i.e., do we say
S|- (B&~B) and S|=(B&~B), i.e., we can both derive syntactically
(i.e., have a proof of) B&~B from S, and have a model for S in which
B&~B is true?
Thanks.
in Sentence Logic and in Predicate Logic?
I know in Sentence Logic, that a sentence ( a Wff, actually) S is
contradictory, if from S we can derive (using theorems of
truth-functional logic ) a sentence of the type A&~A , where '&'
is 'and' and '~' stands for negation, i.e., we assume S, and, using
theorems, we can conclude, using MP, that S->(A&~A).
How do we define contradiction in Predicate Logic, tho? Is it
defined both syntactically and semantically, i.e., do we say
S|- (B&~B) and S|=(B&~B), i.e., we can both derive syntactically
(i.e., have a proof of) B&~B from S, and have a model for S in which
B&~B is true?
Thanks.