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Linglib.Theories.Pragmatics.Assertion.Krifka

Krifka: Commitment Space Semantics and Layered Assertive Clauses #

@cite{krifka-2015} @cite{krifka-2020}

Combines two strands of Krifka's work:

  1. Commitment spaces: the discourse state is a tree — the root (√C) is the current CG, and continuations are proposed future states from questions. Assertion narrows every state (C + S⊢φ); questions preserve the root and add branches (C + ?φ). Per-agent commitment slates track individual public commitments, enabling the commitment/belief separation (lying, hedging).

  2. Layered assertive clauses: four syntactic layers each contributing a distinct semantic dimension:

LayerContributionExample Modifier
TPPropositional contenttense, aspect
JP (Judge Phrase)Epistemic judgment"I think", evidentials
ComP (Commitment Phrase)Commitment strength"I swear", "perhaps"
ActP (Act Phrase)Speech act typedeclarative, imperative

JP and ComP are independent: "I think I swear p" vs "I swear I think p" both involve TP content p, but with different epistemic/commitment profiles.

Commitment Space Tree #

The discourse state is a CommitmentSpace tree (§4):

CommitmentSpace = { root : List Prop, continuations : List (List Prop) }

The four syntactic layers of an assertive clause.

Ordered from innermost (TP, propositional content) to outermost (ActP, speech act force). Each layer contributes a distinct semantic dimension that can be independently modified.

TODO: @cite{krifka-2015} §4 also posits PolP (Polarity Phrase) between ComP and TP, hosting verum (⊢) / falsum (⊣). High negation at ComP (¬⊢φ = non-commitment to φ) vs TP negation (⊢¬φ = commitment to ¬φ) explains the bias asymmetry of negative questions: "Isn't it raining?" is biased toward rain because negation scopes over ⊢, not over φ.

  • TP : ClauseLayer

    Tense Phrase: propositional content

  • JP : ClauseLayer

    Judge Phrase: epistemic status (certainty/uncertainty)

  • ComP : ClauseLayer

    Commitment Phrase: commitment strength

  • ActP : ClauseLayer

    Act Phrase: speech act type

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      Graded commitment strength, controlled by ComP modifiers.

      • weak: hedged ("I think p", "maybe p")
      • standard: default declarative assertion
      • strong: oath formulae ("I swear p", "I promise p")
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          A fully layered assertion, decomposed into the four clause layers.

          Each layer is independent: the epistemic status (JP) can vary without affecting the commitment strength (ComP), and vice versa. The actType uses IllocutionaryMood from Core/Discourse/DiscourseRole.lean.

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            Agent type for two-participant discourse.

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                A commitment space (@cite{krifka-2015}, Definition 3, p.329).

                A set of commitment states organized as root + continuations:

                • root (√C): the current commitment state — what is actually in the common ground. All worlds compatible with the root propositions are "live".
                • continuations: proposed future states, each extending the root. Added by questions, resolved by acceptance or rejection.

                Krifka's key operations:

                • Assert C + S⊢φ = {s ∩ ⟦φ⟧ : s ∈ C}: narrow every state by φ
                • Question C + ?φ = {√C} ∪ (C + S₂⊢φ): preserve root, propose φ
                • Accept: take a continuation as the new root
                • Reject: prune a continuation

                The tree structure captures the assertion/question asymmetry: assertions modify the root (the CG changes), while questions only add continuations (the CG is preserved until acceptance).

                • root : List (BProp W)

                  Root commitment state √C: propositions currently in the CG

                • continuations : List (List (BProp W))

                  Proposed future states. Questions add these; acceptance promotes one to root. Each continuation is a list of propositions that extends (narrows) the root.

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                  The empty commitment space: no commitments, no continuations.

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                    Assert φ: narrow every state by φ (@cite{krifka-2015}, (9), p.329).

                    C + S⊢φ = {s ∩ ⟦φ⟧ : s ∈ C}

                    Adds φ to the root AND all continuations. Any accepted continuation will also entail φ.

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                      Question: preserve root, propose φ (@cite{krifka-2015}, (14), p.332).

                      C + ?φ = {√C} ∪ (C + S₂⊢φ)

                      The root stays unchanged (CG preserved). A new continuation is added (root narrowed by φ), and existing continuations are also narrowed by φ. The addressee can accept (promote continuation to root) or reject (prune it).

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                        The space is settled: no open continuations. A settled space has no unresolved proposals.

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                          Accept the first continuation: it becomes the new root. The CG is updated to the accepted proposal's content.

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                            Reject the first continuation: prune it. The CG is unchanged; the proposal is discarded.

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                              Context set from root: worlds compatible with all root propositions.

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                                Assertion preserves settledness.

                                Question makes a settled space unsettled (adds a continuation).

                                Accepting a simple question's sole continuation re-settles.

                                Root after assertion contains the asserted proposition.

                                Question preserves root commitments.

                                Krifka's discourse state: per-agent commitment slates + shared commitment space (tree).

                                The commitment space tracks the shared discourse structure: what's in the CG (root) and what's been proposed (continuations). Per-agent slates track individual public commitments, enabling the commitment/belief separation central to Krifka's theory.

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                                  Initial state: no commitments, empty settled space.

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                                    Krifka's commitment operator + S₁⊢p (@cite{krifka-2015}, (9)): speaker commits to p, narrowing the entire space.

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                                      Accept: addressee also commits to p (after speaker's assertion).

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                                        Assert = commit (@cite{krifka-2015}: assertion IS commitment). The space is narrowed immediately; the CG reflects the assertion.

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                                          Question: speaker proposes φ as a continuation (@cite{krifka-2015}, (14)). The CG (root) is unchanged; a new continuation is added.

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                                            Accept the first continuation: it becomes the new CG.

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                                              Reject the first continuation: prune it.

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                                                Retract: remove a commitment from the speaker's slate.

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                                                  Context set: from the commitment space root (= CG).

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                                                    Stability: the space is settled (no open proposals).

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                                                      theorem Theories.Pragmatics.Assertion.Krifka.comp_preserves_content {W : Type u_1} (la : LayeredAssertion W) (str : CommitmentStrength) :
                                                      { content := la.content, epistemicStatus := la.epistemicStatus, commitmentStrength := str, actType := la.actType }.content = la.content

                                                      ComP preserves TP content: changing commitment strength does not change the propositional content.

                                                      theorem Theories.Pragmatics.Assertion.Krifka.jp_comp_independent {W : Type u_1} (la : LayeredAssertion W) (ep cs : CommitmentStrength) :
                                                      { content := la.content, epistemicStatus := ep, commitmentStrength := cs, actType := la.actType }.content = la.content { content := la.content, epistemicStatus := ep, commitmentStrength := la.commitmentStrength, actType := la.actType }.commitmentStrength = la.commitmentStrength { content := la.content, epistemicStatus := la.epistemicStatus, commitmentStrength := cs, actType := la.actType }.epistemicStatus = la.epistemicStatus

                                                      JP and ComP are independent: changing one does not affect the other.

                                                      Krifka's ActP layer directly uses IllocutionaryMood, grounding the clause-type distinction in the speech act classification.

                                                      Update type for assertions.

                                                      Krifka distinguishes two fundamentally different ways an assertion can change the common ground:

                                                      • informative (·φ): eliminates worlds incompatible with φ. c + ·φ = {i | i ∈ c ∧ φ(i)} Example: "The meeting is at 5" — reduces uncertainty.

                                                      • performative (•φ): changes world indices so φ becomes true. c + •φ = {i' | ∃ i ∈ c, i ⇒_φ i'} Example: "I hereby name this ship the Queen Elizabeth" — makes φ true by the act of uttering it.

                                                      This distinction is orthogonal to commitment strength (ComP) and epistemic status (JP).

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                                                          Informative update: restrict context set to worlds satisfying φ. @cite{krifka-2020}, (7): c + ·φ = {i | i ∈ c ∧ φ(i)}

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                                                            A fully specified assertion with update type.

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                                                              Default assertions are informative (the common case).

                                                              Commitment Closure (@cite{krifka-2020}, (25)): assertion immediately narrows the commitment space. The root (CG) after asserting φ is the original root with φ prepended.

                                                              In the tree model, this is definitional: assert adds φ to all nodes including the root.

                                                              Questions don't change the CG: the root is preserved.

                                                              Question then accept ≈ assert (on the root): accepting a question's sole continuation yields the same CG as a direct assertion.

                                                              This connects the two modes of updating: direct assertion (speaker imposes) and question-then-accept (speaker proposes, addressee accepts). The roots match because both produce φ :: root₀.

                                                              The two discourse roles in a speech act.

                                                              Every speech act has an actor (who performs the act) and a committer (who undertakes the commitment). These can diverge:

                                                              • Assertion: actor = speaker, committer = speaker
                                                              • Monopolar question: actor = speaker, committer = addressee (the speaker proposes that the addressee commit)

                                                              This is the "one promising aspect" Krifka highlights in his conclusion: the framework naturally separates who acts from who commits, explaining why questions can be biased (the speaker chooses WHAT to propose) without being assertive (the addressee decides WHETHER to commit).

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                                                                    In monopolar questions, speaker acts but addressee commits. @cite{krifka-2015}, (16): C +_{S₁} [? [⊢ p]] proposes that S₂ commit to p.

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                                                                      A speech act in Krifka's framework: ActP content with its discourse function (assertion vs question).

                                                                      @cite{krifka-2015} clause structure: ActP > ComP > TP (three layers). The 2020 paper refines this to ActP > ComP > JP > TP.

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                                                                        Monopolar question: proposes a single continuation where the addressee commits to φ.

                                                                        C +_{S₁} [? [⊢ φ]] = {√C} ∪ (C + S₂⊢φ)

                                                                        The root is preserved ({√C}) alongside the proposed continuation (C + S₂⊢φ). The addressee can accept (take the continuation) or reject (stay at root). This is what makes it a QUESTION rather than an assertion — the commitment is proposed, not imposed.

                                                                        Monopolar questions are inherently biased toward the proposed continuation.

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                                                                          Complex speech act: conjunction or disjunction of atomic acts.

                                                                          @cite{krifka-2015}, §5: question tags involve composition of speech acts. The difference between matching and reverse tags is conjunction vs disjunction:

                                                                          • conj: both acts performed sequentially (matching tag)
                                                                          • disj: addressee chooses one continuation (reverse tag)
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                                                                            A matching question tag: conjunction of assertion + monopolar question with same content.

                                                                            "It's raining, isn't it?" = speaker asserts rain AND asks addressee to confirm. The speaker has already committed, so the question is biased toward the asserted content.

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                                                                              A reverse question tag: disjunction of assertion + monopolar question with opposite content.

                                                                              "It's raining, or isn't it?" = speaker offers two continuations. The addressee picks one.

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                                                                                In a matching tag, the assertion and question share content.

                                                                                In a matching tag, the speaker is actor in both acts.

                                                                                In a matching tag, the committers differ: speaker for assertion, addressee for question.

                                                                                Matching tags are conjunctions, reverse tags are disjunctions.