Modern definitions of technology focus upon the mechanical arts or applied sciences, while studies of invention and innovation range from industrial research and development laboratories to business management. They underline the difficulty of addressing ancient technology with concepts relevant to antiquity. Lynn White Jr. observed that ‘no Greek or Roman ever told us, either in words or in iconography, what he or his society wanted from technology, or why they wanted it’, and the problem of definition is exacerbated by relative judgements made about its success or failure. Although concepts of progress can be found in ancient philosophy, a long consensus amongst historians of technology was that the few items that can be claimed as Greek or Roman inventions were not exploited, and that this failure was attributable to social factors. A potent assertion maintained by many commentators on supposed advances in medieval technology is that Rome could not be liberated from animism before its conversion to Christianity, after which labour and production began to be valued. As with ‘Darwinian’ concepts of ancient technology which assume that technical progress was a natural path of development towards the Industrial Revolution, such monocausal explanations are unsatisfactory on empirical and theoretical grounds. If we must judge ancient technology, should success be measured by showing that inventions known from documentary sources actually existed, or should we demand that they were widely and productively employed? Whose needs should we consider—the state, the army, a social élite, or the multitude?Most elements of Graeco-Roman technology were either inherited from prehistoric times, or adopted from ‘barbarian’ peoples.