This treatise deals with some fundamental issues of the Shi'a Islamic faith. Although not all the chapters were written at the same time, they are interrelated and connected by the theme of imamate and wilayat of the Imams of Ahlul Bayt. Chapter 2 was written in 1998, chapter 3 in 1990, chapter 4 in 1997, while the first and last three chapters have been written this year. While revising chapter 3, the section 'The Meaning of Mawla' was added by the author to complete the discussion on Ghadir Khumm. It is hoped that the reader will gain some insight into the Shi'a Islamic point of view on the most fundamental issue that has defined its existence in the past as well as in the present. This book also reflects some issues that are being discussed among some sections of the Shi'a community in North America. Such discussions and debates, at the least, provide the opportunity to further study and clarify the essential beliefs of Shi'a Islam.