Traditionally, the knowledge base has been defined more as product than process and has encompassed definitions, principles, values, and facts. Recent reforms in teaching and teacher education have brought about efforts to redefine the knowledge base. The reconceptualized knowledge base builds upon the earlier model but gives higher priority to reflective thinking, actively exploring problems, and learning from experts. While furnishing a constructivist knowledge base for such a vision is problematic, teacher educators might consider five areas of focus as a scaffolding for reform: (1) autobiography, intended to increase awareness of oneself and one's beliefs; (2) inquiry, an ongoing exploration of complex questions; (3) reflection, which draws on intuitive knowledge to synthesize understandings into a new and fuller form; (4) critique, which sees teacher educators and teachers as critical, even political, thinkers who consider decisions about content and method to be value judgments, not just rational management decisions; and (5) community, the development of jointly constructed, productive connections for sharing and overcoming problems. As applications of some aspects of this newer view of the knowledge base, four commonly cited problems for second language teacher education are discussed: fragmentation, tensions between language-based coursework and courses in pedagogical and professional development, the theory-practice gap and the role of field experiences, and the tension between the training and development of language teachers. (32 references) (AMH)