The main purpose of this article is to illustrate John Dewey's methodology of reflective thinking highlighted in How We Think (1933), and thereby investigate its implications for principles of teaching. Firstly, the author analyzes the content of reflective thinking, from three angles: incentives of thinking, attitudes toward thinking, and methods of thinking. Secondly, the author systematically describes the connections between reflective thinking and teaching. He points out that in Dewey's mind, an ideal model of teaching should at least include four attributes: being positive, purpose-oriented, complete, and continuous. Lastly, the author offers a critical reflection on Dewey's thinking methodology. He concludes that reflective thinking based on scientific method is not the only thinking model that Dewey takes to be valuable. It is only when we can utilize scientific thinking as well as humanistic thinking that we can comprehend the whole picture of life and safeguard our dwelling place.