Drawing on Dewey's critique of the way educators, historically, have tried to promulgate definitive prescriptions for educational practice, this article examines implications of the use of science for supervisory practice and for the field of supervision as a whole. A content analysis of Dewey's "The Sources of a Science of Education" indicates the pervasiveness of the technocratic nature of teaching and supervision. Historical evidence is presented to indicate the degree and manner to which educators have tried to use science to justify inspectional and prescriptive practices of supervision. The significance of Dewey's work is in the realization that science alone should not dictate supervisory practice. Rather, viewing science with more tentativeness and exploration is needed. Lessons from Dewey's work are discussed, as are implications for the field of supervision.