Critical Study on Voltaire's Views about Muhammad's Personality

François-Marie Arouet (Voltaire) (1694-1778) as a most controversial orientalist in 18th century, expressed challenging views about Islam and Life of Prophet (Sira) which have undergone a gradual evolution. Initially, in the first phase he has a highly critical view on Islam and Muhammad such that he has addressed him as a liar and deceitful man. In the second phase which synchronizes with the middle of his cultural and scientific life he adopted a moderate stance on Islam and Muhammad. In this phase he has introduced the prophet as a politician and finally late in life, he has praised and worshipped the prophet and has referred to him as creator of the biggest revolution and religion and mentions Islam as the greatest religion. Thus, this paper aims to illustrate the thinking of Voltaire about Muhammad, the way he was transformed and its causes and this study also seeks to answer the following questions: 1. What is the reason of Voltaire’s critical attitude towards Muhammad? 2. In which issues he criticizes Muhammad? 3. What factors are involved in transforming Voltaire’s outlook on Muhammad? 4. Is there any relationship between his positive view on Muhammad in the second half of his life and his critical attitude towards Christianity?