Although it is one of the most commonplace terms in the modern lexicon, “fashion” proves difficult to define, controversial to analyze, and moreover tends to inspire demonstrations of scorn or devotion. There is the impression both that it exists to different degrees in different times and places, and that today's urban fashion is more urgent and omnipresent than that of former days or less developed areas. Yet when it comes to declaring where fashion is absent, such as in primitive, ancient, or medieval cultures, scholars who know those cultures will frequently claim its presence. To come to terms with this problem and be able to speak with a common analytical vocabulary, there is a need for a set of criteria that represent the basic necessary conditions that must be present if fashion's various aspects coalesce to become a dominant system in a culture, a “fashion system,” to appropriate Roland Barthes’ term. Such criteria would help explain many of the otherwise inexplicable behaviors and products found in fashion-dominated cultures. They would offer a structure for analyzing trends in many objects of consumption, and in particular a way of perceiving the value of objects produced in great imitative quantities which were obviously popular in their own time, but which have been dismissed by later generations as derivative and unoriginal.

Though long considered a superficial frivolity, when fashion becomes systematically embedded in a society it connects many levels of life – from the collective economy to personal psychology – in a self-renewing cycle of creativity and production. Its existence in a culture has far-ranging significance.

Most commentators on fashion up to fairly recently have characterized it as either trivial or decadent. It was long classified among the minor arts, those not making lasting contributions to civilization, ranking even lower in status than the decorative arts. Individual fashion trends, such as vogues for tight leggings or sewn sleeves, may not produce lasting contributions to society, but I would argue that the mechanisms of trade, creativity and production that various vogues bring into being have shaped economies and cities. Fads may be minor, but fashion systems have a major bearing on civilization.