Islamic contributions to the Hellenistic study of chemia not only created the word alchemy but also laid the foundations for the development of chemistry. Islamic medical discoveries and writings were significant and proved influential in later periods. We look at the natural philosophical and intellectual components of two groups of Arabic thinkers, the falasifa and the mutakallimun. We examine the reasons given by scholars for the decline of Islamic intellectual pre-eminence in the 13th century.