This book offers a solution for the problem of structure and agency in
sociological theory by developing a new pair of fundamental concepts:
metric and nonmetric. Nonmetric forms, arising in a crowd made out of
innumerable individuals, correspond to social groups that divide the
many individuals in the crowd into insiders and outsiders. Metric forms
correspond to congested zones like traffic jams on a highway:
individuals are constantly entering and leaving these zones so that they
continue to exist, even though the individuals passing through them
change. Building from these concepts, we can understand "agency" as a
requirement for group identity and group membership, thus associating it
with nonmetric forms, and "structure" as a building-up effect following
the accumulation of metric forms. This reveals the contradiction between
structure and agency to be a case of forced perspective, leaving us
victim to an optical illusion.