For centuries following the fall of Rome, Western Europe was backward and benighted, locked into the Dark Ages and barely able to tell the time of day. Augustine had decreed that belief, not reason, should be the guiding light of Christian thinking and partially as a result Europeans lived in a world of nominal literacy and subsistence farming, where blind faith, superstition and sorcery took the place of medicine, and the church harnessed nascent aggression among the kingdoms to its own ends in the pursuit of astonishingly violent and cruel holy wars - the Crusades. Arab culture, however, was thriving, and had become a powerhouse of intellectual exploration and discussion that dazzled the likes of Adelard of Bath who ventured to the Near East in search of the scientific riches pouring out of cities like Antioch or Baghdad, whose House of Wisdom held four hundred thousand books at a time when the best European libraries housed, at most, several dozen. The Arabs could measure the earth's circumference, a feat not matched in the West for eight hundred years; they discovered algebra; were adept at astronomy and navigation, developed the astrolabe, translated all the Greek scientific and philosophical texts including, importantly, those of Aristotle; they made paper lenses and mirrors. Without them, and the knowledge that travellers like Adelard brought back to the West, Europe would in all likelihood have been a very different place over the last millennium.