标签：#chomsky

A useful technical idea, repeated often enough, eventually generates an unuseful philosophical claim. The current example is grammar-constrained decoding. The technique is straightforward — at each generation step, the language model's next-token logits are masked so that only tokens whose continuation can satisfy a formal grammar remain selectable; the output is, by construction, structurally valid. JSON parses. SQL is well-formed. Function-call signatures match. There is a real engineering payoff and a healthy ecosystem of libraries that deliver it. The drift is not in the engineering. It is in the rhetorical move that follows the engineering. A growing corner of 2025-2026 AI writing argues, more or less explicitly, that constraining a model's output is making the model approach meaning — that filtering linear sequences is somehow building structure, and that structure is somehow building understanding. I want to take that drift seriously, because it is the same conflation Chomsky and collaborators flagged in their March 2023 essay in the New York Times , and the engineering literature on constrained decoding agrees with Chomsky on the substantive question, even when the marketing copy doesn't. What grammar-constrained decoding actually is A language model produces output one token at a time. At each step, the model emits a probability distribution over its vocabulary, and the decoding strategy (greedy, top-k, nucleus, etc.) picks one token. Without modification, the model is free to emit any continuation; the resulting text might happen to be valid JSON, or it might not. Grammar-constrained decoding intervenes in that step. A formal grammar — typically a context-free grammar, sometimes a regular expression, sometimes a JSON schema or Pydantic model — defines what counts as valid output. At each generation step, the constraint engine computes which next tokens could lead to a continuation that is still satisfiable under the grammar, masks the logits for all other