This self-study of teacher education practices explores an emerging teacher educator's development as a supervisor of teacher candidates. The purpose was the development of a rationale for teaching and teacher education that reflected his exploration of a personal understanding of purpose in social studies teaching and teacher education. With the help of a critical friend, he engaged in a process in which he could reflect upon prior experiences, develop insights into existing research, and engage in discussions that helped frame and inform developing practice. By applying the question 'What do we teach for?' the teacher educator developed an emerging context-based rationale for teacher education practices. In focusing on his development as a university supervisor, the emerging teacher educator was better able to assist student teachers in their development of rationale-based practice. The insights and understandings shared in this article add to research about the teacher candidate supervision process.