Abstract: This chapter begins by outlining the various challenges faced by the massive modularity hypothesis, most of which turn on one or another form of cognitive flexibility. It outlines the role of mental rehearsal and inner speech in explaining stimulus independence, and it explores how language may play a role in integrating contents deriving from modular systems that would not otherwise communicate with one another. It outlines a two-systems theory of human reasoning processes, and explains how cycles of inner speech might serve to realize the operations of System 2. It also contrasts the views being defended with a variety of other proposals concerning the role of language in human cognition.

Keywords: cognitive flexibility, content integration, inner speech, language, mental rehearsal, stimulus independence, two-systems theory of reasoning,