The study focuses on Clark W. Hetherington who has been considered to be an outstanding philosopher and scientist in the field of physical education. The purposes of this study are as follow. It deals with his ideological position and role; his academic achievement and philosophy; and important philosophical theories. To sum up the results of the research, firstly, when Hetherington was strongly involved in physical education, the "New Physical Education" era began to rise among scholars including Thomas Wood, Rosalind Cassidy and Luther Gulick. These scholars fascinated history of physical education in America. Hetherington led the era of New Physical Education and contributed to scientific systematization of physical education. Secondly, after investigating his life, he was a logical academic and perfectionist. His educational ideal was influenced by a psychological theory of play which was founded by S. Hall. It is clear that he was true scientist and philosopher who established an academic foundation of physical education in the early 20C. Thirdly, among other things, he provided a theoretical framework of New Physical Education and its base was Dewey's pragmatism which eventually helped Hetherington's idea to launch the Demonstration Play School. He also strongly believed that play activities including various games, sports and recreational activities could impact on the youths' character building. Lastly, his educational ideal was again influenced by the progressivism and pragmatism and his main philosophical theory was play theory. Thus, play could lead children's all-around education. It was him to stimulated the American society to consider to place physical education in schools' curricula. It was him to articulate "the New Physical Education" meaning that physical education should be a form of scientific and whole education for the youth and the adult. The significant results of this study could be that Hetherington was a true scientist and philosopher. He stressed the importance of play activities in the development of the youth; believed that leaders and teachers of physical education should be trained in a scientific educational curriculum to meet the needs of the youth and the adult; regarded health as a balance of the physical and mental conditions; and finally he considered physical education was a fundamental education, total education and character education in order to promote the development in childhood - his life long objective in the promotion of program in physical education. Considering his great achievements in American physical education, appropriate expressions, 'the Modern Philosopher and Father of Physical Education' can be followed with his significant contribution.