The problematic of the milieu begins with the French word sens. Mesology takes on the task of establishing the concrete links between these three levels of sens that are generally separated in other disciplines. Hence the neologism mediance, initially defined as “a milieu’s sens” in the French triple acceptation. Subjectity appears with life and continues developing to the point of producing the self-referential being of the cogito. The scales of the trajective chain’s evolution are metrical in the sense that they can be measured in time and space; for instance, neither in time nor space is the evolution of the species Homo sapiens of the same scalar order as the history of the Thirty Years’ War. The living are capable of combining the first and second meanings of the word sens, while inanimate matter can only move in the sense of direction.