Are there Hilbert-style Pure Type Systems?

For many a natural deduction style logic there is a Hilbert-style logic that is equivalent to it in that it has the same theorems (i.e. valid judgements with empty contexts). For intuitionistic logic, the axioms of the equivalent Hilbert-style logic can be propositions which are also known as the types of the combinators I, K and S. Hilbert-style versions of illative combinatory logic have formulations with axioms that are actual type statements for I, K and S. As pure type systems (PTSs)are, in a sense, equivalent to systems of illative combinatory logic, it might be thought that Hilbert-style PTSs (HPTSs) could be based in a similar way. This paper shows that some PTSs have very trivial equivalent HPTSs, with only the axioms as theorems and that for many PTSs no equivalent HPTS can exist. Most commonly used PTSs belong to these two classes. For some PTSs however, including lambda* and the PTS at the basis of the proof assistant Coq, there is a nontrivial equivalent HPTS, with axioms that are type statements for I, K and S.Comment: Accepted in Logical Methods in Computer Scienc

S (for Syllogism) Revisited: "The Revolution Devours its Children"

In 1978, the authors began a paper, “S (for Syllogism),” henceforth [S4S], intended as a philosophical companion piece to the technical solution [SPW] of the Anderson-Belnap P–W problem. [S4S] has gone through a number of drafts, which have been circulated among close friends. Meanwhile other authors have failed to see the point of the semantics which we introduced in [SPW]. It will accordingly be our purpose here to revisit that semantics, while giving our present views on syllogistic matters past, present and future, especially as they relate to not begging the question via such dubious theses as A →’ A. We shall investigate in particular a paraconsistent attitude toward such theses

On the construction and algebraic semantics of relevance logic

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2020, Director: Joan Gispert Brasó[en] The truth-functional interpretation of classical implication gives rise to relevance paradoxes, since it doesn't adequately model our usual understanding of a valid implication, which assumes the antecedent is relevant to the truth of the consequent. This work gives an overview of the system $\mathbf{R}$ of relevance logic, which aims to avoid said paradoxes. We present the logic $\mathbf{R}$ with a Hilbert calculus and then prove the Variable-sharing Theorem. We also give an equivalent algebraic semantics for $\mathbf{R}$ and a semantics for its first-degree entailment fragment

Some Locally Tabular Logics with Contraction and Mingle

Anderson and Belnap’s implicational system RMO can be extended conservatively by the usual axioms for fusion and for the Ackermann truth constant t. The resulting system RMO is algebraized by the quasivariety IP of all idempotent commutative residuated po-monoids. Thus, the axiomatic extensions of RMO are in one-to-one correspondence with the relative subvarieties of IP. An algebra in IP is called semiconic if it decomposes subdirectly (in IP) into algebras where the identity element t is order-comparable with all other elements. The semiconic algebras in IP are locally finite. It is proved here that a relative subvariety of IP consists of semiconic algebras if and only if it satisfies x ≈ (x → t) → x. It follows that if an axiomatic extension of RMO has ((p → t) → p) → p among its theorems then it is locally tabular. In particular, such an extension is strongly decidable, provided that it is finitely axiomatized

Differential Semantics

Differential Semantics is a theoretical accounting of the semantic complexity found in natural language, particularly that of the academic and literary registers. It addresses natural language semantics in terms of its contribution to the characterization and expression of creative thought, beginning the perception and conceptualization of objective reality, folloby the metacognitive development of idiosemantic connotations in reference to those conceptualizations, and finally, the intuitive process of implication and inference that facilitates the abstraction and communication of thought