Born in Germany • Birth year 1948 • Studied Mathematics at the Universities of Münster and Tübingen • Habilitation in Mathematics • Lives in Düsseldorf, Germany • Senior Professor of Mathematics Education at the University of Duisburg-Essen
I enjoyed math at school because I was good at the problems and really liked the inner clarity and regularity of the subject.
The transition to university mathematics was extremely difficult for me at first because I had to overcome a huge gap. But after a year, I made a breakthrough, and from then on, I gained a foothold and my appreciation for the subject grew steadily.
I had my first experience of deep amazement when I was preparing for a linear algebra exam. When studying Jordan normal forms, I suddenly realized what a magnificent overview this provided of what initially seemed to be an overwhelming variety of matrices, and what potential mathematical theory formation can unfold in terms of intellectual organization.
The interplay between mathematical content and questions and observations about how people deal with it in work processes was to become an important guiding principle for my future career
In the second part of my studies, I had the opportunity to participate in a working group led by my future doctoral supervisor I and was able to listen to the insider communication between advanced members. This gave me important insights into what motivates professional mathematicians—which questions they find interesting and which methods and results they consider remarkable, how they base their assessments on these, but also which informal, often metaphorical means of communication they use in the run-up to formally elaborate representations. These experiences have greatly enriched my relationship with mathematics. The interplay between mathematical content and questions and observations about how people deal with it in work processes was to become an important guiding principle for my future career.
It so happened that I was assigned a dissertation topic that also involved a classification problem (four-dimensional quadratic division algebras over p-adic fields), and so a bow was drawn back to my first experience of admiring a mathematical achievement. While working on this, I also learned how inevitably successful problem solving in mathematics can depend on the favor of a good idea. You can prepare the ground for helpful ideas through persistent work, but you cannot force them. I was very grateful that productive ideas for solutions did eventually come to me in time.
(…) I read a lot of mathematical literature and noticed with regret that, over the course of history, presentations had become more sober and formal, and that human emotions and accompanying epistemological considerations had been largely stripped away in the face of mathematical discoveries
During my doctoral studies, I read a lot of mathematical literature and noticed with regret that, over the course of history, presentations had become more sober and formal, and that human emotions and accompanying epistemological considerations had been largely stripped away in the face of mathematical discoveries. The more I missed this aspect, the more my interest grew in the question of how mathematical knowledge develops in an individual, what thought processes and attitudes play a role in this, and how consciousness is refined during these processes. These were the reasons why I turned to mathematics education after completing my doctorate, and fortunately, life gave me the opportunity to make this field my profession.
After a long career, I am convinced that at every level of learning, it is possible to create an authentic picture of mathematics and convey an impression of how mathematics forms its own world of well-ordered structures with a striking internal consistency, and how this is precisely what makes it so effective in applications.
Published on January 14, 2026.
Photo credit: FAU/Ianicelli/Aslanidis