This is the first book in the English language that focuses on Mulla Sadra's groundbreaking theory of transubstantial motion. In this work, the author offers a comprehensive and erudite discussion on Mulla Sadra's theory and how it has influenced other spheres of philosophy. In the first part of the book, the background of transubstantial motion is discussed and compared to similar views in occidental philosophy. In Part 2, Prof. Dehbashi translates Mulla Sadra's famed chapter on transubstantial motion from the fourth volume of his magnum opus, Al-Asfar al-Arba'ah.