This article examines a key feature of Denis Bouchard's Sign Theory of Language, namely the Substantive Hypothesis (SH), the idea that “the most explanatory linguistic theory is one that minimizes the elements (ideally to zero) that do not have an external motivation in the prior properties of the perceptual and conceptual substances of language”. The article argues that the strongest form of the SH is challenged by two widespread classes of phenomena: morphosyntactic generalizations that are not sign-based, and non-sign-based external pressures on grammars. It concludes with some speculative remarks on why, to a significant degree, grammatical patterning is not sign-based.
