Volume 4 of the collected writings of Viktor von Weizsäcker includes his most famous work, "The Gestalt Circle," which has been translated into several languages, as well as essays and lectures that can be regarded as direct preparatory works, deepening studies, or supplements to the "Theory of the Unity of Perception and Movement." These contributions, spanning the years 1931 to 1948, focus partly on the experimental and partly on the theoretical or philosophical domains, thus reflecting the breadth of the main work, which was first published in 1949.