• README ⤓ .txt 2026-10-22T165042.936 000000000000720
  Logics in which necessarily equivalent formulas are not interchangeable. A possible-worlds semantics identifies a proposition with a set of worlds, and that identification is what makes 2+2=4 and every other necessary truth the same proposition. The entries here refuse it, and each refuses it by replacing the point of evaluation or the semantic value with something finer: a partial state that exactly verifies, an impossible world where classical laws fail, a content or subject-matter that a formula is about.
• Aboutness ⤓ .md 2026-10-22T090936.000 000000000042288
  Stephen Yablo, Aboutness (2014), building on Lewis's "Statements Partly About Observation" (1988) and Perry's earlier work on subject matter. The thesis: a sentence has a subject matter distinct from its truth condition, and the difference does explanatory work — in confirmation, in what a partial truth gets right, in why "the King of France is bald" fails differently from "2+2=5".
• Analytic Implication ⤓ .md 2026-08-20T065642.000 000000000052680
  William Tuthill Parry, "Ein Axiomensystem für eine neue Art von Implikation (analytische Implikation)" (Ergebnisse eines mathematischen Kolloquiums, 1933), written out of Menger's Vienna colloquium: a conditional that holds only when the consequent's content is already contained in the antecedent's. Dunn (1972) gave the first algebraic treatment and a modification of the system. Kit Fine, "Analytic implication" (Notre Dame Journal of Formal Logic, 1986), supplied a semantics and a completeness proof. Angell's analytic containment (1977, 1989) is the sibling relation, and Thomas Macaulay Ferguson's Meaning and Proscription in Formal Logic (2017) places the family alongside Bochvar's logic of nonsense.
• Containment Logic ⤓ .md 2026-10-22T092925.000 000000000036736
  Angell's analytic containment (1977, 1989) and Parry's earlier proscriptive principle are the ancestors. The modern systems: Fine's truthmaker semantics for exact entailment and containment (2016, 2017); Correia's account of factual equivalence and containment (2004, 2010); Yablo's Aboutness (2014), where containment is subject-matter inclusion. Ferguson's Meaning and Proscription in Formal Logic (2017) surveys the family.
• Essence and Accident ⤓ .md 2026-08-20T065744.000 000000000048896
  Kit Fine, "Essence and Modality" (Philosophical Perspectives 8, 1994), which argued that the modal account of essence — x is essentially F iff necessarily x is F if x exists — gets the extension wrong, and that essence should be understood as real definition. Fine's "The Logic of Essence" (Journal of Philosophical Logic, 1995) gave the formal system and "Semantics for the Logic of Essence" (2000) the models. Fabrice Correia's work on essence, generalized essence, and ontological dependence is the main systematic alternative. The programme reverses the traditional order of explanation: modality is defined from essence rather than essence from modality.
• Ground ⤓ .md 2026-10-22T092923.000 000000000034384
  Kit Fine, "Guide to ground" and "The pure logic of ground" (2012); Correia, "Grounding and truth-functions" (2010) and later work; Schnieder, deRosset. The formal side of the metaphysical grounding literature: a consequence relation for "because" in its explanatory rather than causal sense, where the disjunction is grounded in the disjunct and not the reverse.
• Impossible Worlds ⤓ .md 2026-10-22T180154.561 000000000000776
  Routley's non-classical worlds (1980) and Rescher–Brandom (1979); Priest's development (1997, 2005); Nolan's defence of impossible worlds (1997); Berto and Jago's Impossible Worlds (2019) is the standard treatment. Extension of possible worlds. Worlds where contradictions hold. Non-trivial impossible reasoning. Hyperintensional semantics.
• Situation Semantics ⤓ .md 2026-10-22T180154.561 000000000000864
  Jon Barwise and John Perry, Situations and Attitudes (MIT Press, 1983), following Barwise's "Scenes and other situations" (1981). The driving argument was linguistic: naked-infinitive perception reports — "Ralph saw Mary run" — permit substitution of coreferring terms and support existential generalization, yet fail to be closed under logical equivalence, which no possible-worlds semantics can deliver. Keith Devlin, Logic and Information (1991), gave the infon algebra; Barwise and Etchemendy, The Liar (1987), applied the framework to semantic paradox using Aczel's anti-foundation axiom; Barwise and Seligman, Information Flow (1997), developed the constraint machinery into channel theory.
• Truthmaker Semantics ⤓ .md 2026-08-20T020402.000 000000000034896
  Fine (2010s). Exact verification. States as truthmakers. Hyperintensional. Foundation of exact semantics.
• CRITERIA ⤓ .txt 2026-10-22T165042.936 000000000000736
  Not sufficient: Being non-truth-functional, since every intensional operator is that (Modal). A modal operator over a Kripke frame, however fine the accessibility conditions—a frame still identifies a proposition with a set of worlds, and necessary equivalents stay interchangeable (Modal). A third truth value or a degree (Algebraic). Failing a classical law for any reason other than the fineness of the semantic value.