This study is a phenomenology of the practice of high school teaching. It is an examination of the day-to-day lived experience of high school teachers. The research is grounded in Heidegger's (1962) theory of hermeneutic phenomenology, as well as Polanyi's (1961) theory of tacit knowing. The study uses a phenomenological research design influenced by Moustakas (1994) and Creswell (2007), which includes interviews and observations of participants and the identification of themes and sub-themes in their statements and practices. The study also includes a scholarly personal narrative of the researcher's teaching experience. The findings of this study identify four main themes that run through the lived experience of teaching. The first theme, purpose, includes the inherent skills and the love of content that draws teachers to the profession, the values that underlie their decisions and actions, and the resignation they experience when reconciling their idealistic notions of teaching with the reality of the classroom and the educational system. The second theme, structure, is about the order and form that teachers try to give a sometimes chaotic context, as well as the balance and flexibility needed to deal with the chaos, and the limits and restrictions outside of a teacher's control. Teachers also talk about their interactions with students and colleagues--the third theme--including meaningful relationships, issues of power and authority, and autonomy and collegiality. The fourth theme, emotion, runs through the other three themes. This study examines the teachers' metaphorical understanding of their practice, as well as how teachers negotiate the tensions between the various themes, their ideals of teaching and the reality of the classroom, and their organic understanding of teaching within a mechanistic system. This study also examines how the theory of tacit knowing helps explain the process of integration that teachers develop through experience. Finally, the study examines the implications of this research in the areas of teacher training and professional development. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]