This article aims to reflect the trajectory of the teacher from the perspective of building and rebuilding the knowledge of the professional in education; it shows the teacher constituting the development of his knowledge-substance and knowledge-practice over the course of teacher performance, which makes each professional unique, though they consist of the same feelings and the same needs. These perspectives are made salient in the view of authors such as Tardif, Maués, and others. The methodological proposal used is naturalistic-constructive. This article deals with the difference between a mathematician and a Mathematics teacher, and highlights the aspects relevant to classroom practices in this discipline. The importance of practices that are reflective, critical and allied to theory is also highlighted. The characteristics pointed out in the text with respect to teacher education evidence the need for general cultural education, that is, the education of a "civilized man". This characteristic, when constructed, enables the Mathematics teacher to relate the content of this discipline to the daily situations of the student's life, thereby establishing the meaning of the discipline for the student.