- with S4 Modal
Semantics
The semantics for predication, quantification, and truth-functional operators are the same as .
Modal Operators
For modality, we reuse the crunch function from quantification:
Crunched Value
The crunched value of v is 1 (T) if v is 1, else 0 (F).
Possibility
The value of a possibility sentence ◻A at is the maximum of the crunched values of its operand at each world such that is in .
This is in accord with interpreting the possibility operator in terms of generalized disjunction.
Necessity
The value of a necessity sentence ◻A at is the minimum of the crunched values of its operand at each world such that is in .
This is in accord with interpreting the necessity operator in terms of generalized conjunction.
includes the access relation restrictions on models of :
Reflexivity
In every model, for each world , is in the access relation.
Transitivity
In every model, for each world , and each world , for any world such that and are in the access relation, then is in the access relation.
Tableaux
tableaux are constructed just like system tableaux.
Nodes
Nodes for many-valued modal tableaux come in two types:
A node consisting of a sentence, a designation marker (⊕ or ⊖), and a world.
An access node like , indicating that the pair is in the access relation .
Trunk
To build the trunk for an argument, add a designated node with each premise at world , followed by an undesignated node with the the conclusion at world .
Closure
Rules
contains all the rules, and adds modal operator rules, as well as the access rules.
Modal Operator Rules
◇ Rules
◻ Rules
Access Rules
Operator Rules
⚬ Rules
¬ Rules
∧ Rules
∨ Rules
⊃ Rules
≡ Rules
→ Rules
- →⊕Conditional Designated[source]
- A → B ⊕, w0⋮¬A ∨ B ⊕, w0A ⊖, w0B ⊖, w0¬A ⊖, w0¬B ⊖, w0
↔ Rules
Quantifier Rules
∃ Rules
∀ Rules
Notes
References
Doug Owings (2012). Indeterminacy and Logical Atoms. Ph.D. Thesis, University of Connecticut.