For Freudenthal, the practice of mathematics in the curriculum is not a set of predetermined theories, goals and means. On the contrary, it is always associated with positively understood phenomenological processes in mathematics, as the curriculum is often used in conjunction with the transformation or development of practice. For Freudenthal (1968), educational theory was a practical endeavour from which new theoretical ideas could emerge as a kind of scientific by-product. In his view, curriculum development should not take place from the academic ivory tower, but in schools, in collaboration with teachers and students. He expressed similar ideas and, by calling for a practical curriculum, eloquently questioned curriculum theory in research and development and innovation.