There is some difference in the approach of a biographer and a historian. A biography is usually an exercise in hero worship. A biographer is prone to paint the picture of his hero in bright colors. The approach of a historian is basically objective and constructively critical. Every hero of a biographer may not necessarily be a great man from the point of view of history. Where the hero is a great man in history, his biography has to be projected in the context of history. Ali is verily a great man of the history of mankind in general and history of Islam in particular. In undertaking this study in the life of Ali, I have to act not merely as a biographer but as a historian as well. This means that besides narrating the main events in the life of Ali, I have to examine the impact of such events on history. As such I have to subject the main events in the life story of Ali to critical examination to ascertain their causes and effects. Of course such criticism has to be constructive.