The work is a critical exposition and analysis of Mulla Sadra's theory of Transubstantial Motion, one of Sadra's most innovative contributions to Islamic philosophy. The writer explains how the theory of substantial motion bridged the physical and spiritual aspects of reality and how Sadra solved the philosophical dilemmas of his era. Also included is a translation of "Al-Afsaar Al-Arba'ah"(The four spiritual journeys) in which Mulla Sadra presents his theory and takes the reader through a rewarding discourse on the nature of space and time, a discourse only fully appreciated in the light of modern physics. P/B pgs. 231