The routine activity approach offers us a few simple concepts that can then be elaborated. These concepts are based on the tangible legal activities of ordinary people, setting the stage for illegal events to occur. The focus is on events, not offenders themselves. The concepts are elaborated step by step, culminating in a recent book, Crime and Nature. Yet the simplest ideas remain the foundation: Crime is a very tangible activity feeding on other tangible activities. Major changes and variations in crime occur without requiring shifts in human inclinations. These concepts help us study crime with the most important branch of mathematics--arithmetic.
Some of the major concepts:
minimal elements of crime,
convergences and divergences of these elements,
crime’s three main stages: prelude, event, aftermath,
diagramming criminal acts,
thick crime habitat,
crime symbioses, mutualisms, parasitisms,
foraging by offenders and other participants,
crime’s defenses, and
the street-gang strategy.