 Fodor (1998b) does offer an empirical argument in favor of systematicity. The idea is that if complex expressions could be understood without understanding their constituents then it is unclear how exposure to a corpus made up almost entirely of complex expressions could suffice to learn the meanings of lexical items. But, as a matter of empirical fact, children learn the meanings of words by encountering them almost exclusively within other expressions. However, as Robbins (2005) points out, this observation can at best lead one to conclude that understanding a suitably large set of complex expressions in which a given expression occurs as a constituent suffices for understanding the constituent itself. It does not show that understanding any complex expression suffices for understanding its constituents.