Denying God for almost 60 years, Antony Flew, the famous analytic philosopher, announced that he believes in God based on some scientific evidences. According to Flew, his conversion was happened to fulfill this principle in his life: “follow evidence, wherever it leads you”.In the period of his atheism, on the basis of certain issues such as the existence of evils in the world and the meaningfulness of the religious statements, Flow challenges the views of the theists and on the basis of the presupposition of atheism put the responsibility of offering reason on their shoulders. But as regard the atheists he has the same position. Accordingly, he neither considers himself as a theist nor positive atheist. He considers his position as negative atheism. Hence his belief in the time of atheism was provisional. As a result, in the light of new findings in the field of genetics and on the basis of the principle of his reason he declared that he believes in God. But his opponents, chiefly on the basis of their prejudices, sought to consider his return from atheism as stemmed from his old age, weakness of memory, and defect of his knowledge. In this article, while referring to the basic thought of Flow in periods of atheism and theism, the authors try to carry out a critical study of the views of the opponents and prove that his conversion did not contradict his basic principle.