This article offers the author's commentary on the Multiple Grammar (MG) language acquisition theory proposed by Luiz Amaral and Tom Roeper in the present issue and touches on other second language acquisition research. Topics discussed include the concept of second language (L2) optionality, a hypothesis regarding the acquisition of the English language by German or Dutch native speakers, and a hypothesis regarding the acquisition of modern Spanish by English or Chinese speakers. In this commentary, the author refers to previous L2 research dealing with optionality in order to: (1) determine whether and how the specific implementation of the Multiple Grammar Theory (MGT) proposed by Amaral and Roeper would deal with those issues; and (2) to discuss representational views of L2 optionality which indirectly address the so-called 'comparative fallacy', or the idea that interlanguage grammars should be studied as systems in their own right (Bley-Vroman, 1989), and the developmental issue of how interlanguage grammars evolve as they develop towards the target.