On the logical substantiveness of compositionality

Abstract

AbstractGiven any set E of expressions freely generated from a set of atoms by syntactic operations, there exist trivially compositional functions on E (to wit, the injective and the constant functions), but also plenty of non-trivially compositional functions. Here we show that within the space of non-injective functions (and so a fortiori within the space of non-injective and non-constant functions), compositional functions are not sufficiently abundant in order to generate the consequence relation of every propositional logic. Logical consequence relations thus impose substantive constraints on the existence of compositional functions when coupled with the condition of non-injectivity (though not without it). We ask how the apriori exclusion of injective functions from the search space might be justified, and we discuss the prospects of claims to the effect that any function can be “encoded” in a compositional one.