Syntax as both Autonomous and Substance-Free

I agree with Buder-Gröndahl, Nóbrega, and Panagiotidis’ (2025) contention that Syntax is radically Substance-Free, in the sense that its primes do not have direct, law-like relationships with the primes of grammar-external cognitive systems. The primes of Phonology and Semantics, on the other hand, I believe do have direct law-like relationships with the primes of grammar-external cognitive systems (those of the sensory-motor system on the one hand, and of the conceptual-intensional system on the other). Despite this, the sensory-motor and conceptual-intensional primes themselves play no role in defining the computations that Phonology and Semantics may carry out. If this is correct, then Phonology and Semantics are not strictly speaking Substance-Free in the same way that Syntax is, but they are Substance-Blind. Furthermore, the primes of Syntax are related to the primes of Phonology and of Semantics by two distinct, orthogonal (but formally parallel) types of rule: Rules of Exponence and Rules of Semantic Interpretation. Since these rules interpret the output of Syntax and do not interfere with the Syntax’s internal computations, it follows that Syntax is Autonomous, as well as Substance-Free.