This book is one of the most distinguished, comprehensive works in the field of Islamic thought in its formative period, based on a critical multidisciplinary approach. In this great voluminous work (six volume), Professor Van Ess focuses on the historical issues and problems in the different areas of the development of Islamic culture and thought. In addition to the wide array of invaluable information and analyses, the book has a specialized comprehensive bibliography as well as an exact system of transliteration. Nevetheless, such a great scholary work with a wide scope of diversity cannot be without inadequacies.