How are we to distinguish between a culture organized around fashion, and one where the desire for novel adornment is latent, intermittent, or prohibited? How do fashion systems organize social hierarchies, individual psychology, creativity, and production? Medieval French culture offers a case study of ”systematic fashion”, demonstrating desire for novelty, rejection of the old in favor of the new, and criticism of outrageous display. Texts from the twelfth and thirteenth centuries describe how cleverly-cut garments or unique possessions make a character distinctive, and even offer advice on how to look attractive on a budget or gain enough spending money to shop for oneself. Such descriptions suggest fashion’s presence, yet accepted notions date the birth of Western fashion to the mid-fourteenth-century revolution in men’s clothing styles. A fashion system must have been present prior to this ‘revolution’ in styles to facilitate such changes, and abundant evidence for the existence of such a system is cogently set out in this study. Ultimately, fashion is a conceptual system expressed by words evaluating a style’s ephemeral worth, and changes in visual details are symptomatic, rather than determinative.