Political life, according to Easton, is a “system of behavior.” At the same time that its elements are interacting with each other, the system as a whole is influenced by and exerts pressure on its environment. Stress is constantly arising within the system and out of its surroundings, and efforts to deal with it result in parametric and even structural variation. The ability of the system to survive depends on the kind of information feedback it receives from its environment, for this is the only channel through which political decision makers can discover which parametric and structural changes are necessary.

More precisely, a political system is a collection of certain kinds of human interactions. These are social in nature and involve both individuals and groups. The distinguishing feature of political interactions is that they are directed toward the authoritative allocation of things that are considered of value within society. Authoritative allocations are accomplished, for example, by physically taking away valued possessions, erecting barriers to prevent their procurement, and providing some individuals or groups with the means for their acquisition. The allocations are authoritative in that individuals and groups consider themselves bound by them. Observing that political interactions as described here appear in many parapolitical groups (such as the family, business firms, and religious and social groups), Easton reserves the term “political system” only for those sets of interactions that are relevant for allocating valued things to a society as a whole.