Response to Jan Hulstijn

The purpose of A Philosophy of Second Language Acquisition is not to dismiss existing theories but to show cognitive and experimental biases in SLA theory and practice. There is a big difference between dismissing theories and showing their biases. This book does not subjectively 'spin' theoretical and research preferences but, rather, thoroughly reviews and examines most relevant theories that fall under three major scientific traditions: behaviourist, cognitive, and sociocultural or dialogic. We need to develop a more comprehensive framework that attempts to unite the two major scientific traditions - cognitive and sociocultural - rather than to deepen the schism that currently exists between them. This calls for building a dialogic and unified framework of SLA. It is a major undertaking because these two traditions represent diametrically opposed views of what it means to be 'scientific.'

The cognitive tradition advocates the search for generalizability, the power of statistical procedures, the uniformity of human mental processes, the universality of rule-governed mental behaviors, the existence of one reality universal to all human beings, the collective mind, an idealized human being placed in a homogeneous external reality speaking with one voice, a giant and complex information processor that runs the program in solitude.

On the other hand, the sociocultural tradition assumes the existence of multiple realties that are interpreted differently by different individuals. These multiple realities exist because human beings are exposed to different sociocultural and institutional settings, where they acquire different voices - different speech genres, in Bakhtin's term. In this tradition, qualitative methods rather than statistically driven quantitative research methods are given a more powerful status. Longitudinal case studies, diaries, journals, and personal narratives are considered to provide important insights into the individual's cognitive development. The investigation of the individual's behaviour, rather than the normalized and homogenized group's behaviour, is considered to represent the locus of scientific inquiry.

To unite these two traditions requires a new theoretical foundation, new research methods, and new ways of teaching and testing second language acquisition. A Philosophy of Second Language Acquisition does not claim to have found a perfect solution, but it does offer an alternative model of SLA. This model is based on combining Vygotsky's sociocultural theory and Bakhtin's literary theory and advocates the use of a variety of research methods, no matter how 'unscientific' they may seem to proponents of the experimental tradition.

The united framework proposed in the last chapter requires freedom to choose from a variety of research methods without being 'persecuted' by those who adhere solely to the experimental tradition. After all, even the field of medicine is not afraid to investigate processes that currently cannot be explained experimentally, such as the effects of prayers on a patient's physical well-being. The fact that something is not experimentally testable at the current state of our knowledge does not automatically mean that it is invalid or should be disregarded.

Can the proposed theoretical model of SLA posited in this book necessarily be discredited because it has not been validated experimentally? There are many examples of models or theories that have been somewhat discredited, but this does not mean that they did not contribute to scientific progress in SLA theory and practice. For example, Krashen's comprehensible input theory, despite its untestable nature, brought about invaluable advances in our understanding of the role of input in SLA. The purpose of a theory is not to provide all the answers but to provide a focus for investigation, a point of reference. The unified and dialogic framework proposed in A Philosophy of Second Language Acquisition provides a useful point of reference for future discussions and investigations of what second language ability is and how it should be investigated, taught, and assessed.