The word civilization comes from the 16th-century French civilisé 'civilized', ultimately from Latin civilis, meaning civil, related to the Latin civis, meaning citizen, and civitas, meaning city or city-state. The foundational treatment of the transition to civilized society is Norbert Elias' The Civilizing Process (1939). In this work, Elias traces the evolution of social mores from medieval courtly society to the notion of civilized society in the Early Modern period. In his book The Philosophy of Civilization (1923), Albert Schweitzer outlined the idea that there are dual opinions within modern society: one regarding civilization as purely material and another regarding civilization as both ethical and material. He stated that the then-current world crisis was due to a humanity having lost the ethical conception of civilization, his own definition of the concept being 'the sum total of all progress made by man in every sphere of action and from every point of view in so far progress helps towards the spiritual perfecting of individuals as the progress of all progress.