This paper examines preservice teacher's views on the function concept. It includes two groups of preservice teachers as they consider the presence of functions in school mathematics. The findings imply that preservice teachers will give issues related to the concept of function low priority in their teaching, and that they require additional support to develop their views on functions. The study illustrates that discussion about fundamental concepts should be an essential component in the preparation of preservice teachers. It also illustrates that reflection on the presence of functions impacts preservice teachers' reasoning, and serves as a starting point for valuable didactical discussions, which are related to subject matter knowledge, pedagogical content knowledge and curricular knowledge.