The starting-point of the thesis was that teachers to a large extent teach on the basis of intuitive theories. This creates a tendency that a number of frequent conceptions, pedagogical and didactic theories, experiences of one's own school days etc. become parts of a more fragmentary structure of ideas, rather than a coherent theory of teaching. With the aim of creating a deeper understanding of questions related to teaching and learning, two dominating perspectives were described initial. By putting the intuitive ideas in relation to basic paradigmatic assumptions a picture was given of what the teacher has to know in order to thoroughly understand a certain perspective. In addition, examples of pedagogical theories were presented that can be referred to the perspective in question, which teachers can adopt to qualify their understanding. A critical discussion of the paradigmatic assumptions paved the way for a third perspective, where thoughts occurring in the other two were partly combined. Here a theoretical basis was also presented to explain why the use of mental tools of thinking, especially such that are linked to knowledge theory may lead the teacher to a more reflective way of dealing with questions of teaching and learning. The third perspective was illustrated, first with four examples of how teaching can be performed, and then also in the form of in-service training for teachers. In the empirical section and in the final conclusion the perspectives were illustrated, discussed and examined critically. On the basis of questionnaires answered by upper secondary school teachers, interviews and observations, assumed examples of intuitive theories were presented. The empirical material was also analysed from the same starting-points as the formulation of the perspectives. Ten teachers' systems of intuitive theories about teaching and learning could thus be constructed. Five of these were presented and a comparison with the perspectives was made. Some analyses, however, turned out to agree best with a further perspective, which had not been focused on in the thesis. It was also found that teachers' practice can be enriched by being confronted with scientific knowledge. The value of such knowledge was illustrated through the evaluation of an inservice programme for teachers.