This book , early Muslim concept of epistemology, is a serious attempt to investigate the elements of knowledge and its sources and its limits in the first Arab and Muslim philosophers. Its a page of a real interaction between Hellenic and Islamic civilizations . The current study based on the original sources and references with very rich analytical footnotes using Arabic, Greek and Latin languages. This study tries to show the considerable role of illumination of creating the mentality of Muslim thinkers such as al-Kindi , al-Farabi and Ibn Sina. This book deserves to be read.