  Debates about category mistakes have substantial implications for some foundational questions in philosophy of language and linguistics. Consider the question of how to formulate the principle of compositionality. It is widely accepted that meaning is in some sense compositional, but there are many non-equivalent ways to elaborate what precisely this amounts to. One hypothesis which originates in the work of Richard Montague but has been substantially developed by Pauline Jacobson (and others), is the idea of  direct  compositionality[31]:  “the hypothesis that the syntax and the semantics work  ‘in tandem’. The syntax builds expressions and the semantics works to assign meanings to the representations as they are built in the syntax” (Jacobson 2012, 109). As Jacobson argues, the hypothesis of direct compositionality is attractive for a number of reasons: it is theoretically parsimonious, unifying the compositional theories of syntax and semantics, and it explains why semantic composition seem to proceed in a local fashion: the meaning of each sub-sentential expression is computed using only the meanings of its syntactic constituents rather than using material in other parts of the sentence. But as Jacobson remarks, “Direct Compositionality entails that there are no syntactic expressions of any sort, which do not have a meaning” (Jacobson 2012, 110). Note that this entails that the direct compositionality hypothesis is inconsistent with the meaninglessness view of category mistakes and thus the question of how to account for the infelicity of category mistakes interacts with the question of which formulation of the principle of compositionality ought to be adopted.