S4GO - GO with S4 Modal


Semantics

The semantics for predication, quantification, and truth-functional operators are the same as GO.

Tableaux

S4GO tableaux are constructed just like KFDE 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 \(w_1Rw_2\), indicating that the pair \(\langle\ w_1, w_2\ \rangle\) is in the access relation \(R\).

Trunk

To build the trunk for an argument, add a designated node with each premise at world \(w_0\), followed by an undesignated node with the the conclusion at world \(w_0\).

To build the trunk for the argument A1 ... An ∴ B write:
A1 ⊕, w0
⋮
An ⊕, w0
B ⊖, w0

Closure

S4GO includes the K3 and FDE closure rules.

⊗K3Glut Closure[source]
A ⊕, w0
⋮
¬A ⊕, w0
⊗
⊗FDEDesignation Closure[source]
A ⊕, w0
⋮
A ⊖, w0
⊗

Rules

S4GO contains all the GO rules, and adds modal operator rules, as well as the S4 access rules.

Access Rules

R+S4Transitive[source]
w0Rw1
w1Rw2
⋮
w0Rw2
R≤TReflexive[source]
A, w0
⋮
w0Rw0

Operator Rules

⚬ Rules
⚬⊕FDEAssertion Designated[source]
⚬A ⊕, w0
⋮
A ⊕, w0
⚬⊖FDEAssertion Undesignated[source]
⚬A ⊖, w0
⋮
A ⊖, w0
¬⚬⊕B3EAssertion Negated Designated[source]
¬⚬A ⊕, w0
⋮
A ⊖, w0
¬⚬⊖B3EAssertion Negated Undesignated[source]
¬⚬A ⊖, w0
⋮
A ⊕, w0
¬ Rules
¬¬⊕FDEDouble Negation Designated[source]
¬¬A ⊕, w0
⋮
A ⊕, w0
¬¬⊖FDEDouble Negation Undesignated[source]
¬¬A ⊖, w0
⋮
A ⊖, w0
∧ Rules
∧⊕FDEConjunction Designated[source]
A ∧ B ⊕, w0
⋮
A ⊕, w0
B ⊕, w0
∧⊖GOConjunction Undesignated[source]
A ∧ B ⊖, w0
⋮
¬(A ∧ B) ⊕, w0
¬∧⊕GOConjunction Negated Designated[source]
¬(A ∧ B) ⊕, w0
⋮
A ⊖, w0
B ⊖, w0
¬∧⊖GOConjunction Negated Undesignated[source]
¬(A ∧ B) ⊖, w0
⋮
A ∧ B ⊕, w0
∨ Rules
∨⊕FDEDisjunction Designated[source]
A ∨ B ⊕, w0
⋮
A ⊕, w0
B ⊕, w0
∨⊖GODisjunction Undesignated[source]
A ∨ B ⊖, w0
⋮
¬(A ∨ B) ⊕, w0
¬∨⊕GODisjunction Negated Designated[source]
¬(A ∨ B) ⊕, w0
⋮
A ⊖, w0
B ⊖, w0
¬∨⊖GODisjunction Negated Undesignated[source]
¬(A ∨ B) ⊖, w0
⋮
A ∨ B ⊕, w0
⊃ Rules
⊃⊕FDEMaterial Conditional Designated[source]
A ⊃ B ⊕, w0
⋮
¬A ⊕, w0
B ⊕, w0
⊃⊖GOMaterial Conditional Undesignated[source]
A ⊃ B ⊖, w0
⋮
¬(A ⊃ B) ⊕, w0
¬⊃⊕GOMaterial Conditional Negated Designated[source]
¬(A ⊃ B) ⊕, w0
⋮
¬A ⊖, w0
B ⊖, w0
¬⊃⊖GOMaterial Conditional Negated Undesignated[source]
¬(A ⊃ B) ⊖, w0
⋮
A ⊃ B ⊕, w0
≡ Rules
≡⊕FDEMaterial Biconditional Designated[source]
A ≡ B ⊕, w0
⋮
¬A ⊕, w0
¬B ⊕, w0
B ⊕, w0
A ⊕, w0
≡⊖GOMaterial Biconditional Undesignated[source]
A ≡ B ⊖, w0
⋮
¬(A ≡ B) ⊕, w0
¬≡⊕GOMaterial Biconditional Negated Designated[source]
¬(A ≡ B) ⊕, w0
⋮
¬A ⊖, w0
B ⊖, w0
A ⊖, w0
¬B ⊖, w0
¬≡⊖GOMaterial Biconditional Negated Undesignated[source]
¬(A ≡ B) ⊖, w0
⋮
A ≡ B ⊕, w0
→ Rules
→⊕L3Conditional Designated[source]
A → B ⊕, w0
⋮
¬A ∨ B ⊕, w0
A ⊖, w0
B ⊖, w0
¬A ⊖, w0
¬B ⊖, w0
→⊖GOConditional Undesignated[source]
A → B ⊖, w0
⋮
¬(A → B) ⊕, w0
¬→⊕GOConditional Negated Designated[source]
¬(A → B) ⊕, w0
⋮
A ⊕, w0
B ⊖, w0
¬A ⊖, w0
¬B ⊕, w0
¬→⊖GOConditional Negated Undesignated[source]
¬(A → B) ⊖, w0
⋮
A → B ⊕, w0
↔ Rules
↔⊕GOBiconditional Designated[source]
A ↔ B ⊕, w0
⋮
A → B ⊕, w0
B → A ⊕, w0
↔⊖GOBiconditional Undesignated[source]
A ↔ B ⊖, w0
⋮
¬(A ↔ B) ⊕, w0
¬↔⊕GOBiconditional Negated Designated[source]
¬(A ↔ B) ⊕, w0
⋮
¬(A → B) ⊕, w0
¬(B → A) ⊕, w0
¬↔⊖GOBiconditional Negated Undesignated[source]
¬(A ↔ B) ⊖, w0
⋮
A ↔ B ⊕, w0

Quantifier Rules

∃ Rules
∃⊕FDEExistential Designated[source]
∃xFx ⊕, w0
⋮
Fa ⊕, w0
∃⊖GOExistential Undesignated[source]
∃xFx ⊖, w0
⋮
¬∃xFx ⊕, w0
¬∃⊕GOExistential Negated Designated[source]
¬∃xFx ⊕, w0
⋮
∀x(¬Fx ∨ ¬(Fx ∨ ¬Fx)) ⊕, w0
¬∃⊖GOExistential Negated Undesignated[source]
¬∃xFx ⊖, w0
⋮
∃xFx ⊕, w0
∀ Rules
∀⊕FDEUniversal Designated[source]
∀xFx ⊕, w0
⋮
Fa ⊕, w0
∀⊖GOUniversal Undesignated[source]
∀xFx ⊖, w0
⋮
¬∀xFx ⊕, w0
¬∀⊕GOUniversal Negated Designated[source]
¬∀xFx ⊕, w0
⋮
∃x¬Fx ⊕, w0
Fa ⊖, w0
¬Fa ⊖, w0
¬∀⊖GOUniversal Negated Undesignated[source]
¬∀xFx ⊖, w0
⋮
∀xFx ⊕, w0

Notes

References