- with S4 ModalSemantics
semantics behave just like includes the access relation restrictions on models ofReflexivity
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
system tableaux.
tableaux are constructed just likeNodes
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 .
To build the trunk for the argument A1 ... An ∴ B write:
A1 ⊕, w0
⋮
An ⊕, w0
B ⊖, w0
Closure
includes theRules
rules plus the access rules.
contains all theAccess Rules
Modal Operator Rules
◇ Rules
◻ Rules
Operator Rules
¬ Rules
∧ Rules
∨ Rules
⊃ Rules
≡ Rules
- ≡⊖Material Biconditional Undesignated[source]
- A ≡ B ⊖, w0⋮A ⊖, w0¬B ⊖, w0¬A ⊖, w0B ⊖, w0
→ Rules
- →⊕Conditional Designated[source]
- A → B ⊕, w0⋮A ⊖, w0¬B ⊖, w0A ⊕, w0¬A ⊕, w0B ⊕, w0¬B ⊕, w0
↔ Rules
- ↔⊕Biconditional Designated[source]
- A ↔ B ⊕, w0⋮A ⊖, w0B ⊖, w0¬A ⊖, w0¬B ⊖, w0A ⊕, w0¬A ⊕, w0B ⊕, w0¬B ⊕, w0
- ↔⊖Biconditional Undesignated[source]
- A ↔ B ⊖, w0⋮A → B ⊖, w0B → A ⊖, w0
Quantifier Rules
∃ Rules
∀ Rules
Compatibility Rules
⚬ Rules
Notes
References
Priest, Graham. An Introduction to Non-Classical Logic: From If to Is. Cambridge University Press, 2008.