Some recent research in foreign-language education has suggested that many of the activities teachers traditionally engage in are either useless, or worse, counterproductive. From Krashen 1981' and 1982 and from sources cited therein one might easily conclude that foreign-language teachers should not teach anything. They should simply present the language naturally and comprehensibly. Then, given sufficient input under favorable affective conditions, each student's natural language acquisition device is activated, and spontaneous, fluent, and accurate use of the target language results. A close reading of the literature of "input hypotheses, " however, shows that they apply most strongly to immersion environments, not to the more circumscribed contact opportunities typical of most high school and college language programs. In the latter situations input, however comprehensible, does not attain sufficient density or critical mass to set off "the din in your head."': Instructors in classrooms must be more directive or "interventionist" than they would be in a natural acquisition environment. They must guide their students' attention to the elements of the target language that make communication possible. Such guidance does not imply abandoning acquisition as a goal of instruction; it responds to pedagogical reality. Even accepting that the standard classroom cannot provide a natural, acquisition-rich environment, we can ensure that instruction does not impede or render impossible acquisitionlike progress. One way to do this is to recognize that a grammar is not a collection of forms and paradigms but a system for converting meaning into speech. When instructors focus on the communication of meaning as the goal of instruction, at worst they present their students with a natural motivation for learning the supporting forms. At best, they facilitate the entry of these meaningful forms into the posited language acquisition device. Vocabulary is an area particularly amenable to this type of interventionist guidance. For while adult students may directly acquire concrete and unambiguous vocabulary through demonstration and exemplification, considerable lexical residue, which is more susceptible of direct instructional strategies, remains. In the balance of this article I will discuss first a general strategy for helping students learn and acquire vocabulary, and then, within this context, the specific vocabulary problem of ser versus estar in Spanish. Beginning foreign-language students often have serious misconceptions about language, and in particular, about the role in language played by words. Students intuitively subscribe to what I have called elsewhere the "lexical analog hypothesis," according to which the universal constant across languages is held to be the individual word.4 Students perceive the learning task as replacing one by one a string of native-language words with an analogous string of target-language words. This perception presents foreign-language teachers with a dilemma. We know that the lexical analog hypothesis is fundamentally and demonstrably false, but it is virtually impossible to provide beginning students with an alternative learning strategy. For if we remove English as their fundamental starting point-their stable communicative base--nothing remains with which to replace it. There seems to be no way to get beginning students to stop thinking in English and start thinking in the target language. Yet we can show our students that incrementally they often use the target language directly. After only a short time in Spanish I, students understand and say things like Buenas tardes and Gracias without consciously processing them through two languages. In an interesting sense, they have acquired these parts of the language. If we analyze students' early success with Estoy bien, gracias and Buenas tardes we see that it consists of an admittedly tiny set of expressions that are part of the total system of Spanish, but which students have assimilated into their nascent command of that system. This apparently trivial triumph illustrates the ultimate goal of foreign-language study: a spontaneous linking