Applied linguistics is very much a problem-oriented discipline and therefore necessarily an integrative discipline. I know that it is difficult to define what a ‘problem’ is; there are nevertheless important differences between problem-oriented disciplines and theory-based disciplines, like psychology and linguistics, to take a couple of relevant examples. Activities, including research, carried out in the name of applied linguistics should throw light on the processes and conditions and phenomena of language acquisition, language learning or language use, with the aim of contributing to the solution of the difficulties and practical problems that arise. And the problems that people face in connection with language learning or language use are messy, that is to say, like all real life situations they are not analysable in term of only one basic discipline. The chief requirement on research within such basic disciplines is that it should throw light on theoretical models and issues, and to do that the researcher abstracts from the experential world only those special aspects which are interesting to him. People who work in applied disciplines have to deal with complex real life situations as they are, as they are seen to be by the participants in those situations, and have to draw on whatever background disciplines that are relevant and available. (That nearly always means that more than one researcher has to be involved.)