The computations of the mind rely on the structural organization of phrases but are blind to the linear organization of words that are articulated and perceived by input and output systems at the sensorimotor interface (speech/sign). The computational procedure that is universally adopted is computationally much more complex than an alternative that relies on linear order.

Linear order is not available to the systems of syntax and semantics. It is an ancillary feature of language, probably a reflex of properties of the sensorimotor system that requires it for externalization, and constrained by conditions imposed by sensorimotor modalities.

It follows that language is primarily an instrument for the expression of thought. Language is neither speech/sign (externalized expression) nor communication (one of its many possible uses).