This article presents aunified logicthat combines classical logic, intuitionistic logic and affine linear logic (restricting contraction but not weakening). We show that this unification can be achieved semantically, syntactically and in the computational interpretation of proofs. It extends our previous work in combining classical and intuitionistic logics. Compared to linear logic, classical fragments of proofs are better isolated from non-classical fragments. We define a phase semantics for this logic that naturally extends the Kripke semantics of intuitionistic logic. We present a sequent calculus with novel structural rules, which entail a more elaborate procedure for cut elimination. Computationally, this system allows affine-linear interpretations of proofs to be combined with classical interpretations, such as the λμ calculus. We show how cut elimination must respect the boundaries between classical and non-classical modes of proof that correspond to delimited control effects.

This paper modifies our previous work in combining classical logic with intuitionistic logic [16, 17] to also include affine linear logic, resulting in a system we call Affine Control Logic. A propositional system with six binary connectives is defined and given a phase space interpretation. Choosing classical, intuitionistic or affine reasoning is entirely dependent on the subformula property. Moreover, the connectives of these logics can mix without restriction. We give a sound and complete sequent calculus that requires novel proof transformations for cut elimination. Compared to linear logic, classical fragments of proofs are better isolated from non-classical fragments. One of our goals is to allow non-classical restrictions to coexist with computational interpretations of classical logic such as found in the λμ calculus. In fact, we show that the transition between different modes of proof, classical, intuitionistic and affine, can be interpreted by delimited control operators. We also discuss how to extend the definition of focused proofs to this logic.

We show that control operators and other extensions of the Curry-Howard isomorphism can be achieved without collapsing all of intuitionistic logic into classical logic. For this purpose we introduce a unified propositional logic using polarized formulas. We define a Kripke semantics for this logic. Our proof system extends an intuitionistic system that already allows multiple conclusions. This arrangement reveals a greater range of computational possibilities, including a form of dynamic scoping. We demonstrate the utility of this logic by showing how it can improve the formulation of exception handling in programming languages, including the ability to distinguish between different kinds of exceptions and constraining when an exception can be thrown, thus providing more refined control over computation compared to classical logic. We also describe some significant fragments of this logic and discuss its extension to second-order logic.

We present a compact sequent calculus LKU for classical logic organized around the concept of polarization. Focused sequent calculi for classical logic, intuitionistic logic, and multiplicative-additive linear logic are derived as fragments of LKU by increasing the sensitivity of specialized structural rules to polarity information. We develop a unified, streamlined framework for proving cut-elimination in the various fragments. Furthermore, each sublogic can interact with other fragments through cut. We also consider the possibility of introducing classical-linear hybrid logics.