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Linglib.Theories.Semantics.Modality.ActualityEntailments

Actuality Entailments: Position × Aspect #

@cite{hacquard-2006} @cite{hacquard-2009} @cite{bhatt-1999} @cite{nadathur-2023}

Bridges event-relative modality (EventRelativity.lean) with the causal frame (ComplementEntailing.lean) to derive actuality entailments from the relative scope of aspect and modal.

The Puzzle #

The same modal verb shows different entailment patterns depending on interpretation (@cite{bhatt-1999}, @cite{hacquard-2006} Ch.1):

@cite{hacquard-2006}'s Solution #

The relative position of the modal determines which event binder captures it:

Bridge to @cite{nadathur-2023} #

ComplementEntailing.lean formalizes the causal model: ability modals are CausalFrame World with actualization = .aspectual.

Content Licensing Explains the Asymmetry #

WHY are epistemic modals always above aspect? Content licensing (EventRelativity §8): epistemic modal bases require a contentful event. VP events lack content. Therefore epistemic modals cannot be bound by aspect — they must be above AspP. Root modals need only circumstantial backgrounds (any event type), so they CAN be below AspP.

The actuality entailment asymmetry follows from content licensing + aspect scope, without stipulation.

The relative scope of aspect and the modal in the clause structure.

Root modals are below AspP: aspect quantifies over the modal event. Epistemic modals are above AspP: the modal quantifies over aspect.

This structural difference — not lexical semantics — is the sole source of the actuality entailment asymmetry.

  • aspectOverModal : AspectModalScope

    Root: [Asp [Mod [VP]]] — aspect scopes over modal

  • modalOverAspect : AspectModalScope

    Epistemic: [Mod [Asp [VP]]] — modal scopes over aspect

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      Whether the theory predicts an actuality entailment for a given position × aspect combination.

      Only root + perfective yields an actuality entailment:

      PositionAspectAE?Why
      root (below Asp)PFVAsp > Mod: PFV forces completion
      root (below Asp)IMPFAsp > Mod: IMPF doesn't force completion
      epistemic (above Asp)PFVMod > Asp: PFV in accessible worlds only
      epistemic (above Asp)IMPFMod > Asp: no completion
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        Only root + perfective yields actuality entailments. This is a characterization result: AE ↔ (belowAsp ∧ perfective).

        The prediction aligns with the aspect scope story: AE holds exactly when aspect scopes over the modal AND aspect is perfective.

        The same lexical modal yields different actuality patterns depending solely on position. This is Hacquard's core argument against lexical ambiguity: French pouvoir, Greek boro, Hindi saknaa are single lexical items whose actuality behavior is structurally determined.

        ComplementEntailing.lean formalizes the causal semantics: ability modals are CausalFrame World with actualization = .aspectual. The bridge:

        - `actualityWithAspect .perfective w` = `sufficientAt w ∧ actualizedAt w`
          → captures the root + PFV case
        - `actualityWithAspect .imperfective w` = `sufficientAt w`
          → captures the root + IMPF case
        
        The theorems below make this correspondence explicit. 
        

        The causal model (Nadathur) and the structural account (Hacquard) agree: the causal model explains WHY perfective ability entails the complement; the structural account explains WHY this arises only for root modals.

        WHY are epistemic modals always above aspect? Content licensing (EventRelativity §8) provides the answer:

        The chain: content licensing → position → scope → (no) AE.

        The actuality entailment pattern results from a three-way interaction between content licensing, syntactic position, and viewpoint aspect.

        This theorem chains together:

        • EventRelativity §8 (content licensing determines available flavors)
        • EventRelativity §9 (position determines event binder)
        • This file §1–2 (position determines aspect scope → AE prediction)
        • ComplementEntailing.lean (causal model validates the root + PFV case)