Constructivism is considered one of the most attractive theoretical foundations within educational science and is a highly relevant concept in practice. It not only provides extraordinarily plausible explanations of the processes of knowledge and learning but also proves to be very fruitful for the design of pedagogical action concepts. This book offers, on one hand, an introduction to the most important variations of constructivism and a critical engagement with them. However, this is not an end in itself. On the other hand, the effectiveness of constructivism in its different variants and themes is explored as a foundational theory for pedagogy. To this end, the positions of educational directions that identify themselves as constructivist or influenced by constructivism are examined. Thirdly, it is clarified whether and how constructivism can be stimulating for pedagogy.