Implementing practical religious rules in his personal and social life, a Muslim is approaching secrets of eternal bliss and supreme realities of the universe. In fact, these rules are the result of God's knowledge. B rilliant representatives of Islam's juristic heritage found their final formulation in religious sources - through a professional process called ijtihad. In order to get to know the subject of these rules, they were necessarily focused on empirical achievements and social contexts of their time. Under the influence of the dominant modern science, Muslim reformers identify ijtihad with empirical research. In this way, they reject sublime and unchanging cognitive bases of ijtihad, which comprise religious revelation and rational knowledge. However, they ignore the fact that modern science has absolutely no power to judge all the realities and values as scientists from XIX century naively wanted. In this paper, we try to follow fundamental changes in the meaning of ijtihad, primarily using a detailed content analysis of popular works of two famous Muslim reformist thinkers, Muhammad Iqbal and Ali Shariati. The former insists that today only modern, empirical knowledge has scientific credibility and that it is the only one to follow in all aspects of life. In the works of the latter, we read that in the light of ijtihad, Islam has to change and go in line with modern science and new social needs.