In L2 research, it is agreed that learners must develop an implicit mental representation of language. However, there is debate as to how this implicit system develops. Of interest to the present discussion is what can be called the explicit/implicit debate: to what extent is explicit learning implicated in adult second language acquisition? The question has largely centered on formal properties of language, generally called “rules” and “forms.” Proponents for some role of explicit learning argue that learners (must) somehow engage explicit processes in extracting rules and forms from the input they are exposed to. Proponents for implicit learning argue that explicit processes are not engaged.