Research on second language (L2) acquisition in the generative tradition (GenSLA) addresses the nature of interlanguage competence, examining the roles of Universal Grammar, the mother tongue and the input in shaping the acquisition, representation and use of second languages. This field is sometimes dismissed by applied linguists as irrelevant because it does not provide direct applications for language teaching. However, the assumption that theories must have applications involves a fundamental misconception: linguistic theories explore the nature of grammar; GenSLA theories explore the nature of language learning. No such theory entails that language must be taught in a particular way. Nevertheless, potential applications can be identified: examples are presented that describe aspects of language that do not need to be taught, properties that might benefit from instruction, and cases where textbooks provide inadequate information. I argue that linguistic theory and GenSLA theory have more to offer in terms of considering what aspects of language might or might not be taught rather than how languages should be taught.

生成传统 (GenSLA) 中第二语言 (L2) 习得的研究解决了中介语能力的本质，研究了通用语法、母语和输入在塑造第二语言习得、表现和使用方面的作用。这个领域有时被应用语言学家认为是无关紧要的，因为它不提供语言教学的直接应用。然而，假设理论必须有应用涉及一个基本的误解：语言理论探索语法的本质；GenSLA 理论探索语言学习的本质。没有这样的理论意味着必须以特定的方式教授语言。尽管如此，还是可以确定潜在的应用：所提供的例子描述了不需要教授的语言方面、可能从教学中受益的特性，以及教科书提供的信息不充分的情况。我认为，语言学理论和 GenSLA 理论在考虑可以或不可以教授语言的哪些方面而不是应该如何教授语言方面可以提供更多。