This article presents an English translation (from the German) of one of gestalt psychology's most significant documents, first published in 1920 in Wolfgang Kohler's Die physischen Gestalten in Ruhe und im stationdren Zustand (The Physical Gestalten at Rest and in a Stationary State). The book it introduces both embodies Kohler's extension of gestalt theory into new domains and did much to ensure the broad impact of these ideas and approaches. This introduction itself well illustrates Kohler's own thought processes both as his ideas emerged and as he sought to convince his readers of their value. Despite the fact that they are more than 70 years old, Kohler's words have many implications for late 20th century discussions of the relationships among psychology, physiology, and physics.