Why do I have to deal with theories, I just want to become a teacher? This is the question asked by student teachers in the educational sciences and subject didactics. The articles in the volume 'Theories! Horizons for Teacher Education' offer an answer to this question: On the one hand, our society needs a discussion about the overall orientation of its educational goals and also a fruitful debate within the educational sciences and the related sciences of school subjects. At a time of political, social and cultural upheaval in the field of education, the need for an orienting reflection is becoming increasingly important. Theory discourses are the place for this self-orientation. Student teachers must then be enabled to think from multiple perspectives. They can learn this best by engaging with theories. The individual contributions in this volume show what theories make visible in a new way and what, on the other hand, they close off when they are received in a one-sided or totalizing way. After all, theories have a genuine heuristic power; theories make things visible, they open doors, they allow us to understand something anew. Accordingly, the contributions in this volume ask: Where, whether in educational science or subject didactics, can we find examples of "aha" moments or of an understanding of larger contexts that only become possible through theoretical penetration? What do we see in the world, in our lives and as a phenomenon in a completely new way once we have understood a theory?