The paper deals with the issue of critical areas in the philosophy as part of the subject Basics of Social Sciences in the Czech Republic from the perspective of teachers. The critical areas are components of the curriculum that are difficult, challenging and problematic for educational practice. They can be on the side of both teachers and students and cause problems with teachers' didactic transformation and students' understanding. We investigated how teachers perceive the causes of critical areas on their own side and also on the side of their students. We chose the subject of philosophy in general grammar schools because of its huge time consumption in relation to other social science disciplines taught in Basics of Social Sciences. And we also chose it because of the difficulties in mastering the philosophy curriculum cited by students and teachers. We applied qualitative research based on the grounded theory to analyse the causes of the critical areas from the viewpoint of teachers. To achieve our results, we applied content analysis concerning relevant curricular documents and conducted interviews with 11 teachers. For the analysis of respondents' interviews, open, axial and selective coding methods of grounded theory were applied. The process of obtaining the most general axial codes is introduced, and each axial code is specified in detail. Finally, we applied selective coding to provide a theory for a deeper description of the relationships between axial codes that detected causes of critical areas. The proposed theory may serve for a better understanding of the critical areas origin and understanding of the educational process regularities.