A third approach would regard civilization as an evolving life style, conceived before the earliest days of recorded human history and matured through the series of experiments marking the development of civilization as we have known it during the five centuries from 1450 to 1975. Thinking in terms of this age-old experience, with six or more thousand years of social history as a background, it is possible to give a fairly exact meaning to the word "civilization" as it has been lived and is being lived by the present-day West. It is also possible to understand the history of previous civilizations in cycle after cycle of their rise, their development, decline and extinction. At the same time it will enable the reader to recognize the relationship (and difference) between the words "culture" and "civilization". Human culture is the sum total of ideas, relationships, artifacts, institutions, purposes and ideals currently functioning in any community. Three elements are present in each human society: man, nature and the social structure. Human culture at any point in its history is the social structure: the aggregate of existing culture traits, the products of man's ingenuity, inventiveness and experimentation, set in their natural environment. Civilization is a level of culture built upon foundations laid down through long periods of pre-civilized living. These foundations consist of artifacts, implements, customs, habit patterns and institutions produced and developed in numerous scattered localities by groups of food-gatherers, migrating herdsmen, cultivators, hand craftsmen and traders and eventually in urban communities built around centers of wealth and power: the cities which are the nuclei of every civilization. Urban centers, housing trade, commerce, fabrication and finance, with their hinterlands of food-gatherers, herdsmen, cultivators, craftsmen and transporters, are the nuclei around which and upon which recurring civilizations are built. Within and around these urban centers there grows up a complex of associations, activities, institutions and ideas designed to promote, develop and defend the particular life pattern. A civilization is a cluster of peoples, nations and empires so related in time and space that they share certain ideas, practices, institutions and means of procedure and survival. Among these features of a civilized community we may list: (1) means of communication, record-keeping, transportation and trade. This would include a spoken language, a method of enumeration, writing in pictographs or symbols; an alphabet, a written language, inscribed on stone, bone, wood, parchment, paper; means of preserving the records of successive generations; paths, roads, bridges; a system for educating successive generations; meeting places and trading points; means for barter or exchange;