This book introduces the basic concepts of the classical tradition, and explains how these ideas were promulgated by the ancient Greeks, preserved and commented on by the great Muslim scholars of the early middle ages, and finally transmitted to western Europe as that region began to grow and expand around 1100 C.E. Through biographical sketches of 20 men and women, Christian, Muslim, and pagan, it seeks to provide insight into the lives and accomplishments of people whose works profoundly shaped the era’s scientific spirit. It also attempts to make the case that while the work of these individuals did not seek to overthrow the prevailing worldview of the time, their accomplishments did lay the groundwork for the scientific revolution and European global expansion of the early modern age.