Education is a field of dreams, and so is educational research. Educators dream of schools that can improve the lives of students, solve social problems, and enrich the quality of life; educational researchers dream that their studies will enhance the effectiveness of schools in achieving these worthy goals. Both fields draw recruits who see the possibilities of education as a force for doing good, and that turns out to be a problem because the history of both fields shows that the chances for doing real harm are substantial. Over the years, research on teaching and teacher education--the topic of the discussion in this special issue--has caused a lot of damage to teaching/learning and learning to teach in schools. So the author suggests that a good principle to adopt when considering the role of research in teacher education is a version of the Hippocratic oath: First do no harm. One factor in particular tends to bend the work of researchers toward the dark side of the force, and that is research funding. Another factor that interferes with the educational researcher's desire to do good for teachers and teacher educators is the need to confront an educational version of Gresham's law: Bad research tends to displace good.