Structural Isomorphism of Meaning and Synonymy

In this paper I am going to deal with the phenomenon of synonymy from the logical point of view. In Transparent Intensional Logic (TIL), which is my background theory, the sense of an expression is an algorithmically structured procedure detailing what operations to apply to what procedural constituents to arrive at the object (if any) denoted by the expression. Such procedures are rigorously defined as TIL constructions. In this new orthodoxy of structured meanings and procedural semantics we encounter the problem of the granularity of procedure individuation. Though the identity of TIL constructions is rigorously defined, they are a bit too fine-grained from the procedural point of view. In an effort to solve the problem we introduced the notion of procedural isomorphism. Any two terms or expressions whose respective meanings are procedurally isomorphic are deemed semantically indistinguishable, hence synonymous and thus substitutable in any context, whether extensional, intensional or hyperintensional. The novel contribution of this paper is a formally worked-out, philosophically motivated criterion of hyperintensional individuation, which is defined in terms of a slightly more carefully formulated version of conversion and -conversion by value, which amounts to a modification of Church’s Alternative (A1).