Speech Act Logic

Origin. Searle, Vanderveken (1985). Illocutionary logic. Force and content. Speech act theory formalized. Foundation of pragmatic logic.

Models. Illocutionary forces. Propositional contents. Felicity conditions. Success and satisfaction.

Formalism.

Illocutionary act: F(P): force F applied to content P. F: illocutionary force. P: propositional content.

Force components: Illocutionary point. Degree of strength. Mode of achievement. Content conditions. Preparatory conditions. Sincerity conditions.

Basic forces: ⊢: assertive (commit to truth). !: directive (attempt to get hearer to act). C: commissive (commit speaker to act). D: declaration (make it so). E: expressive (express attitude).

Success conditions: F(P) successful iff: Propositional content conditions met. Preparatory conditions hold. Speaker has required intentions. Hearer recognizes intention.

Satisfaction: F(P) satisfied iff: World matches direction of fit. Assertions: P true. Directives: hearer does P. Commissives: speaker does P.

Direction of fit: Word-to-world: assertions (↓). World-to-word: directives, commissives (↑). Both: declarations. Neither: expressives.

Illocutionary entailment: F₁(P) ⊢ F₂(Q) if success of F₁(P) implies success of F₂(Q). Promise entails commitment.

Indirect speech acts: Literal force ≠ intended force. "Can you pass the salt?" = request. Pragmatic inference.

Symbols.

Symbol	Unicode	Name	Meaning
⊢	U+22A2	Right tack	Assertive force; also illocutionary entailment
↓	U+2193	Downwards arrow	Word-to-world direction of fit, as in assertives
↑	U+2191	Upwards arrow	World-to-word direction of fit, as in directives and commissives
≠	U+2260	Not equal to	Literal force distinct from intended force
!	—	Exclamation mark	Directive force
C	—	Commissive marker	Commissive force
D	—	Declaration marker	Declarational force
E	—	Expressive marker	Expressive force, with null direction of fit
F(P)	—	Illocutionary act	A force applied to a propositional content
F	—	Illocutionary force	The six-component object
P, Q	—	Propositional contents	What the act is about

Metatheory. Searle and Vanderveken's Foundations of Illocutionary Logic (Cambridge, 1985) analyzes a force into six components — illocutionary point, degree of strength, mode of achievement, propositional content conditions, preparatory conditions, and sincerity conditions — and derives the whole inventory of English forces from five points by operations on those components, so promise and vow differ only in strength and mode and are not separate primitives. Two consequence relations fall out rather than one: illocutionary entailment, where success of the first act guarantees success of the second, and satisfaction entailment, which tracks direction of fit and for assertives reduces to ordinary truth-conditional consequence. Vanderveken's Meaning and Speech Acts (Cambridge, 1990–91) develops the resulting logic in two volumes. The framework's structural claim is that force is not truth-conditional content, which is why the semantics is a logic of acts and their success conditions rather than a valuation.

Applies to. Pragmatics. Communication. Agent interaction. Natural language.

Limitations. Force markers do not embed. There is no well-formed conditional whose antecedent is an assertion, so the framework faces the Frege–Geach problem in full and gives no compositional treatment of a speech act inside a larger sentence — which is a large share of the data a semantics of mood must cover. Individuation of forces is underdetermined: the six components admit indefinitely many combinations, and nothing in the theory says which are realized in a language or how to tell two forces apart when their success conditions coincide. Indirect speech acts, the phenomenon the theory is most often invoked for, are handled by inference outside the logic. Commitment is closed under entailment, so an idealized speaker is committed to every consequence of what was asserted. And uptake and perlocutionary effect fall outside the system, which is why dialogue models turn instead to Hamblin's commitment stores (1971) or Lewis's scoreboard (1979).