Most of our information on how teachers of the gifted and talented think while they plan and implement instruction is from the perspective of the researcher, not from the teacher's perspective. One expert teacher was studied in great detail using ethnographic and phenomenological techniques. More specifically, a teacher was studied as he planned and taught two philosophy courses. After extensive observation and interviewing, the teacher's thoughts were categorized into planning thoughts and action thoughts. The author argues that the way in which the teacher's thoughts are linked to his practice cannot be adequately understood unless one gains access to the invisible, tacit knowledge of the teacher. The teacher's hidden world is described in relation to how the researcher discovered it. The concept of professional practical knowledge is discussed in terms of further research and teacher training.