Optionality is a central phenomenon in second language acquisition (SLA), for which any adequate theory must account. Amaral and Roeper (this issue; henceforth A&R) offer an appealing approach to it, using Roeper's Multiple Grammars Theory, which was created with first language in mind but which extends very naturally to SLA. They include in their article some fairly extensive discussion of the relation between their approach and that taken to optionality in the MOGUL framework (see especially Sharwood Smith and Truscott, in press; Truscott, 2006; Truscott and Sharwood Smith, 2004), suggesting that the two are largely compatible and that each can potentially help the other. The two approaches are presented in very different terms, so some translation is needed, and genuine differences exist, but these factors should not be allowed to hide the underlying similarity. In this commentary, John Truscott considers the similarities and differences between these two approaches and, in the process, clarifies some aspects of MOGUL and the approach that it takes to optionality.