Post Completeness and Preconditionals: Three July Papers on Conditional Logic (2026)

The July cluster

Three records from July 22-23 put a specific question back on the table: how should we compare non-classical logics when the comparison concerns not just validity, but the shape of their extensions and the translations that preserve consequence? Giuliano Rosella and Yale Weiss classify maximal consistent extensions of conditional logics. Zhicheng Chen adds a preconditional to fundamental logic and proves completeness, decidability, and modal translation results. Wesley H. Holliday and Guillaume Massas revise a June preprint that places fundamental logic between orthologic, intuitionistic logic, and modal systems. 1 2 3

This is a local methodological cluster, not evidence that philosophical logic as a whole is moving in one direction. Its useful commonality is narrower: each paper makes the preservation or loss of consequence visible under a structural transformation.

Paper	Date status	Main structural result	Citation snapshot
Post Completeness in Conditional Logic	New preprint, July 23	Classifies Post-complete conditional systems and studies the size of the extension lattice.	Semantic Scholar: 0 citations; Google Scholar shows the record without a visible citing-paper count. 4 5
Fundamental Propositional Logic with Preconditional	New preprint, July 22	Adds a lattice-theoretic conditional to fundamental logic, with strong completeness, finite-model property, decidability, and modal embeddings.	Semantic Scholar: 0 citations; Google Scholar shows the record without a visible citing-paper count. 6 7
Fundamental Logic Through the Lens of Modality	Revision 2 on July 23; version 1 was June 29	Gives full-and-faithful translations linking fundamental logic with ortho-S4, intuitionistic KTB, and a modal extension of fundamental logic.	Semantic Scholar: 1 citation; Google Scholar: Cited by 1. 8 9

Conditional logic as an extension lattice

Rosella and Weiss start with the endpoint notion. A logic is Post complete when it is consistent but has no consistent proper extension. In lattice terms, the paper is asking which conditional systems sit at the maximal consistent boundary, and how many such boundary points a base logic has.

The classification is more differentiated than the abstract label suggests. The paper's Theorem 1 identifies exactly nine Post-complete regular conditional logics; Corollaries 1 and 2 reduce the normal and variably strict cases to four and two systems respectively. The broader cases behave differently: the paper proves that Ck has continuum-many seminormal Post-complete extensions and that CK has continuum-many Post-complete extensions. These results, along with analogues of Makinson's embedding theorems, are reported in the paper's full text. 10

That split matters. Finite classification in the regular, normal, and variably strict fragments says that familiar closure constraints can force a small number of maximal positions. The continuum result says that relaxing some of the conditional-specific closure rules does not merely add a few exotic systems; it changes the cardinality of the boundary. The paper therefore gives a way to distinguish a finite taxonomy from a genuinely large extension space.

A preconditional inside fundamental logic

Chen's paper takes the complementary route. Instead of starting with a lattice of completed systems, it asks what happens when a conditional connective is added to fundamental logic, whose propositional core is governed by the introduction and elimination rules for conjunction, disjunction, and negation in a Fitch-style natural-deduction setting.

The added operation is a preconditional: a binary operation on a bounded lattice satisfying five axioms and subsuming Heyting implication, the Sasaki hook on ortholattices, and Lewis-Stalnaker-style conditionals satisfying flattening. Chen presents three systems, K, T, and F, and identifies their algebraic counterparts. For the two stronger systems, the paper constructs a relational semantics and proves strong completeness using a canonical model whose points are pairs of theories. A filtration-style refinement then yields the finite-model property and decidability. 11

The modal part is not an afterthought. Chen extends the GMT-style and Goldblatt-style constructions used by Holliday and Massas so that the preconditional itself receives a translation. On the ortho-S4 side it becomes a boxed Sasaki-hook clause; on the intuitionistic KTB side it becomes a strict intuitionistic conditional. The abstract describes both translations as full and faithful, which means they preserve and reflect derivability rather than merely sending valid formulas in one direction. 2

This gives the connective a structural test. It is not enough that the preconditional can be interpreted in several familiar algebras. The resulting logic must still support a canonical relational account, a finite-model argument, a decision procedure, and translations that do not collapse distinctions in consequence.

Holliday and Massas provide the nearby translation framework, but its date needs care. The record was first submitted on June 29 and revised on July 23, so the July date marks a new version, not a new paper. 3

The paper states three full-and-faithful results. The GMT translation from intuitionistic logic into classical S4 also embeds fundamental logic into ortho-S4. The Goldblatt translation from orthologic into classical KTB also embeds fundamental logic into intuitionistic KTB. A third result sends the relevant intuitionistic fragment into FN4, a modal extension of fundamental logic. The version-2 text also adds a different conditional based on the standard introduction and elimination rules for implication and extends the third theorem to full intuitionistic first-order logic. 12

The role of this paper in the cluster is therefore transport rather than endpoint classification. It shows how a logic can be compared with neighboring systems without treating the comparison as an informal analogy: the translation has to be full and faithful. Chen then adapts that transport mechanism to a new conditional connective. Rosella and Weiss ask a different question about the same broad terrain: once a conditional logic is fixed, what does its space of consistent extensions look like?

What the three papers jointly show

The strongest cross-paper claim is methodological. The three papers put the same object, consequence, under three kinds of pressure:

Boundary pressure: Post completeness asks where consistent extension stops. Its answer can be finite in constrained fragments and continuum-sized when conditional closure is loosened.
Connective pressure: The preconditional paper asks whether adding a conditional preserves completeness, finite representability, decidability, and the distinctions needed for modal translation.
Translation pressure: The modality paper asks whether a weak logic can be embedded into neighboring modal and non-classical systems without losing or gaining derivability.

The resulting picture is not that these papers have discovered one new logic. It is that extension lattices, canonical models, and full-and-faithful translations are three different ways to make the same structural issue inspectable. That is also why the connection should be described as methodological: Chen's abstract explicitly builds on the Holliday-Massas translation work, while the Rosella-Weiss paper develops its own lattice and embedding analysis. The records do not establish a direct response between the two new July papers.

Citation movement: too early for a trend

At the July 26 check, Semantic Scholar lists 0 citations for each of the two new preprints and 1 for the June paper's July revision. Google Scholar shows a visible Cited by 1 link for Fundamental Logic Through the Lens of Modality, while its lookups for the two July preprints show the records but no visible citing-paper count. 4 6 8 9

Those numbers are useful as indexing signals, not as evidence of impact. The two new papers have had only a few days to accumulate citations, and the revised June paper's single citing record is too small to support a ranking or a field-level claim. The substantive signal this week is therefore the concentration of structural techniques, not a measurable citation shift.

Post Completeness and Preconditionals: Three July Papers on Conditional Logic

The July cluster

Conditional logic as an extension lattice

A preconditional inside fundamental logic

What the three papers jointly show

Citation movement: too early for a trend

References

Related content

The July cluster

Conditional logic as an extension lattice

A preconditional inside fundamental logic

The modal transport layer gets revised

What the three papers jointly show

Citation movement: too early for a trend

References

Related content